# Plot Line Curve In R

Loading Unsubscribe from Jeff Hamrick? GOTO 2012 • The R Language The Good The Bad & The Ugly • John Cook - Duration: 38:09. Survival analysis focuses on the expected duration of time until occurrence of an event of interest. If we handed the plot function only one vector, the x-axis would consist of sequential integers. Here is a v vs. Simple Plot Examples in R Below are some simple examples of how to plot a line in R, how to fit a line to some points, and how to add more points to a graph. This ternary diagram displays the packing fraction when three particle types are combined. The colour, width and line texture of the lines drawn by ablinecan be controlled with the col=, lwd=and lty=arguments. Graphics with R draws horizontal lines across the plot at y 1, y 2, y 3 and y 4. The cubic "s" shape is added in. A variety of methods for drawing labels are implemented, ranging from positioning using the mouse to automatic labeling to automatic placement of key symbols with manual placement of key legends to automatic placement of legends. refopts Description line options affect rendition of the plotted expected score and lines. This used to be a quick hack which seems to serve a useful purpose, but can give bad results for functions which are not smooth. The points determined in this way are then joined with straight lines. graphing/test. It builds on top of many existing open-source packages: NumPy, SciPy, matplotlib, Sympy, Maxima, GAP, FLINT, R and many more. The simple scatterplot is created using the plot() function. 4 Adding Disconnected Lines Segments To A Plot The function segmentsadds a set of disconnected line segments to a plot. The R function abline() can be used to add vertical , horizontal or regression lines to a graph. Details The evaluation of expr is at n points equally spaced over the range [from, to] , possibly adapted to log scale. generates a polar plot of a curve with radius r as a function of angle θ. S-curve implies a distribution with long tails. Plotting a scatter plot is extremely easy in R. You may wish to use regression or correlation analysis now. The ylim argument sets the lower and upper limits of the y-axis — ylim = c(0,. Type curves provide a powerful method for analyzing pressure drawdown (flow) and buildup tests. X is the independent variable and Y1 and Y2 are two dependent variables. 100uA), plot the I-V curves. To illustrate some different plot options and types, like points and lines, in R, use the built-in dataset faithful. R adds a table below the plot showing numbers at risk at different times. The data points are generated using random deviate functions in R. how to make plot lines thicker. Any plot or graph that has two axes is an x-y (or bivariate) plot. If the calculations were successful, a scatter plot representing the data will be displayed. geom_smooth will compute a model for you and plot the result directly. The graph plots percentiles of the population on the. qqplot plots the quantiles of varname 1 against the quantiles of varname 2 (Q–Q plot). Matlab has two functions, polyfit and polyval, which can quickly and easily fit a set of data points with a polynomial. I’m going to take 3 series and turn them into stacked filled line plots. Inkscape provides a couple extensions to include function plots in a drawing. With Julianne Hough, Teddy Sears, Penelope Mitchell, Madalyn Horcher. If the plot is to go thru the origin, check the "Set Intercept" box, and enter 0 in the box. There are a couple of reasons for preferring percentile plots to cumulative fractions plots. One vector x (plots the vector against the index vector) > x<-1:10 > plot(x) 2. smooth, a list with two components, x (the grid of evaluation points) and y (the smoothed values at the grid points). This is how you can plot a simple graph using Microsoft Excel. The h= and v= forms draw horizontal and vertical lines at the specified coordinates. Plot symbols and colours can be specified as vectors, to allow individual specification for each point. What is possible is to create a line that appears to a be somewhat smooth curve, provided that a high enough density display is used. where R is the region bounded by the cardioid 4) Compute the area of the region bounded by the two curves x^2 - y^2 = 1 and y = x^2 - 3*x + 1. In the simplest case, we can pass in a vector and we will get a scatter plot of magnitude vs index. Another way of displaying Tumor Response data was discussed earlier in the article on Swimmer Plot. In between is a region of varying uncertainty with more red at one end and more black at the other. It is designed to draw iso-contour of a user-defined function f(x,y). The next two establish the type of plot — type = "l" means line plot (that’s a lowercase “L” not the number 1), and lty = "dotted" indicates the type of line. Program (1): To show curve in same plot for functions f(x) and g(x) is given below in MATLAB. Plotting a function is often helpful to better understand what’s going on. optional vector of times at which to place a confidence bar on the curve(s). What is possible is to create a line that appears to a be somewhat smooth curve, provided that a high enough density display is used. The most frequently reported yield curve compares the three-month, two-year, five-year and 30-year U. Making the Choice Most people have trouble visualizing the meaning of lists or tables of numerical data; unless you're an engineer working in a familiar field, a mathematician used to interpreting matrices, or just plain have the knack for it, groups of numbers hold little obvious information. The smoothness is controlled by a bandwidth parameter that is analogous to the histogram binwidth. I am plotting ROC curves for various datasets. Then as the SO thread answer says you use add = T which tells the plot function to use the current plot and add another line onto it. EAS 199A: Polynomial curve ﬁt Polynomial Curve Fit with Excel 1. fig, ax = plt. This post is all about how to export anti-aliased, high resolution plots from R in Windows. How do I save a plot to an EPS (Encapsulated PostScript) file? DPlot has no direct support for EPS output. 20 (quantitative data) "2) n'2 One sample Proportion (categorical data) Test a claim. TECHNIQUES FOR IMPROVING THE ACCURACY OF CALIBRATION IN THE ENVIRONMENTAL LABORATORY Dennis A Edgerley Quanterra Environmental Services, 880 Riverside Parkway, West Sacramento, California 95605 Abstract Consistent and reliable procedures for generating calibrations are essential to accurate laboratory results. Igor is not designed for this purpose. # load packages suppressMessages(library(reshape2)) suppressMessages(library(drc)) # read in data data <- read. The areas in bold indicate new text that was added to the previous example. In graphing a polar equation of the form r = f() we treat as the independent variable and r as the dependent variable. For example, I often compare the levels of different risk factors (i. abline() is a good choice for this type of line. R includes at least three graphical systems, the standard graphics package, the lattice package for Trellis graphs and the grammar-of-graphics ggplot2 package. prediction - performance - plot [visualizing classifier performance in R, with only 3 commands] ROC curves, precision/recall plots, lift charts, cost curves. A-Plot [ edit ] An A-Plot is a cinema and television term referring to the plotline that drives the story. If you absolutely must have an equation for the trend line of the iso-efficiency curve, you will need to break it into two pieces at the minimum flow point, and correlate each one separately. This corresponds to the graph of the curve passing through the origin in the xy-plane, and our rst task is to determine when this happens. The least squares linear regression line. KaleidaGraph Curve Fitting Features. that a ect all plots in an R session. In a regression classification for a two-class problem using a probability algorithm, you will capture the probability threshold changes in an ROC curve. Two syntaxes are possible: one object of class "roc", or either two vectors (response, predictor) or a formula (response~predictor) as in the roc function. Students can practice creating and interpreting bar graphs on these printable worksheets. A line chart is a graph that connects a series of points by drawing line segments between them. Plotting a function is often helpful to better understand what’s going on. The only difference in the plots is that that it defaults to a curve that goes from lower left to upper right (starting at 0), where survival curves default to starting at 1 and going down. One can rst plot the point’s projections, which is similar to the task of plotting points in the xy-plane, and then use line segments originating from these projections and perpendicular to the coordinate planes to \locate" the point in xyz-space. The aim of this tutorial is to show you how to add one or more straight lines to a graph using R statistical software. plot(roc1, col = 1, lty = 2, main = "ROC") plot(roc2, col = 4, lty = 3, add = TRUE) Also, there is also the pROC::ggroc function for ggplot2 plotting abilities. 5*IQR, where IQR or Inter Quartile Range is the distance between 25th and 75th percentiles. and you will have a nice s-shaped-curve. Then D is calculated from: D = E1 Desired E 5. matplotlib documentation: Multiple Plots and Multiple Plot Features. qnorm plots the quantiles of varname against the quantiles of the normal distribution (Q–Q plot). Ok, I figured out the issue. Airfoil plotter View and plot a full size plan of the airfoil to your chord width. If P is not less than 0. A little tinkering shows that if you don’t do this, subsequent curves get chopped off at the top. Scatterplots in the grid include regression lines, loess curves and the adjusted R-squared statistic. plot the ROC curve: suppressWarnings(lines. Details The evaluation of expr is at n points equally spaced over the range [from, to] , possibly adapted to log scale. The default setting MeshFunctions -> { #1& , #2& } draws an x , y mesh on each surface. Author: Thomas Breloff (@tbreloff) To get started, see the tutorial. The rest of the code is for labels and changing the aesthetics. The discontinuity is immediately visible only if it jumps out of a particular contour level. X Y 1 10 2 20 3 30 4 40 5 50 and I want to find the Y value for X = 10, or X=3. In order to use this data, it must somehow be digitized. The points outside the whiskers are marked as dots and are normally considered as extreme points. Plot Digitizer is a Java program used to digitize scanned plots of functional data. Examples of using Pandas plotting, plotnine, Seaborn, and Matplotlib. While the R-squared is high, the fitted line plot shows that the regression line systematically over- and under-predicts the data at different points in the curve. how to make plot lines thicker. the data is inherited from the plot data as specified in the call to ggplot(). When the fit is good, the value of r 2 is very close to one. Must be specified for symbol drawing. We'll plot a plot with two lines: lines(x, y1) and lines(x, y2). You should read that statement in two parts, the first one clears the value of the IFS variable, i. One of the useful methods of comparing performance of statistical models is Area Under Curve (AUC). This is referred as normal distribution in statistics. The data must be in a data frame. lines in R, there are functions that draw curves. Description Usage Arguments Details Value FURTHER ARGUMENTS Plot title and axis labels Legend title, labels and position Axis limits, breaks and scales Confidence interval P-value Median survival Censor points Survival tables Survival plot height Number of censored subjects barplot Other graphical parameters Author(s) Examples. However I've encountered a small roadblock. The appearance of contour lines can be defined with a line style style in the same manner as plot. Velocity (v) is vertical. if the length of the vector is less than the number of points, the vector is repeated and concatenated to match the number required. Plot definition, a secret plan or scheme to accomplish some purpose, especially a hostile, unlawful, or evil purpose: a plot to overthrow the government. It is a neat little function that provides mathematical plotting, e. R-square can be used to quantify how well a model fits the data, and R-square will always increase when a new predictor is added. The lines in the graph should have been nearly parallel, but non-linearities in the transistor may have caused some variations. Plotting line graphs in R is licensed under a Creative Commons Attribution-Noncommercial-ShareAlike 4. The coef form specifies the line by a vector containing the slope and intercept. ROC curve example with logistic regression for binary classifcation in R. Ok, I figured out the issue. a region (in R2 or R3) is path connected if any two points can be connected by a continuous curve lying in R. Similar to the histogram, the density plots are used to show the distribution of data. Most density plots use a kernel density estimate , but there are other possible strategies; qualitatively the particular strategy rarely matters. Negative values produce left-hand curves, positive values produce right-hand curves, and zero produces a straight line. Pie graphs, or circle graphs, show percentages or fractions of a whole group. measure of the goodness-of-fit for the regression, plotting the residuals as a function of the x-variable is a good way to do this. Curve fitting is the process of constructing a curve, or mathematical function, that has the best fit to a series of data points, possibly subject to constraints. This is equivalent to printing Hello world in other programming languages. Plotting Data with gnuplot This tutorial is intended as a supplement to the information contained on the Physics' Department website: Plotting and Fitting Data and Plotting Data with Kaleidagraph. Plotting data and functions in R drawing the curve (or line, in this case). Unlike points, this can all be specified as a single multi-character string. geom_ribbon allows to build the area around the curve from precomputed values. For example, pnorm(0) =0. The 3-lines C program below shows. Also, do the relations that true_stress = eng_stress * (1+eng_strain) and true_strain = ln(1+eng_strain) still hold true for non-linear cases?. An R community blog edited by RStudio. For example, to draw the curve of a function, there is no function similar to curve(). that a ect all plots in an R session. Plot the "y=" line (make it a solid line for y≤ or y≥, and a dashed line for y< or y>) Shade above the line for a "greater than" (y> or y≥). (The regression line R that appears above was obtained from the least squares regression line by rounding the slope and y-intercept to two decimal places. Typically, aquifer properties are estimated from a constant-rate pumping test by fitting mathematical models to drawdown data through a procedure known as curve matching. Adding Points, Lines, and Legends to Existing Plots Once you have created a plot, you can add points, lines, text, or a legend. In this post we will see how to add. ly sends an incredible number of e-mails about the exceedance (sometimes more than 15 per day). A coördinate axis is a line with coördinates. Density ridgeline plots, which are useful for visualizing changes in distributions, of a continuous variable, over time or space. R-square is a modified version of R-square, which is adjusted for the number of predictor in the fitted line. This function provides a convenient interface to the JointGrid class, with several canned plot kinds. In MATLAB, ultimately every curve is approximated by straight lines or discretized into pixels. Plot the subgroup ranges on the R chart and connect consecutive points with a straight line. Inkscape provides a couple extensions to include function plots in a drawing. 5, or whatever (obviously this is a simplified example) I've been doing the following: Add a trend-line to the scatter plot data; Format the trend-line to one that fits the data (linear in this case). (y = ax 3 +bx 2 +cx+d) Click 'zero' on all four sliders; Set d to 25, the line moves up; Set c to -10, the line slopes; Set b to 5, The parabola shape is added in. # A very nice line plot function for time series data is available in the Mfuzz library. The plot can be classified by response and stage. This is equivalent to printing Hello world in other programming languages. A young woman becomes trapped in her car after a hitchhiker causes her to have an automobile accident. Interactive Plotting with Manipulate. However, it has not covered how to interpret the curves, or how to use them in practice (e. What is possible is to create a line that appears to a be somewhat smooth curve, provided that a high enough density display is used. Most often, line-fitting involves interpolation or is used for extrapolation of data for prediction of future catastrophic events. Each line is. However, you're still missing an essential part of your standard curve in Excel – the "line" part of the line graph. The slope of the tangent line at a cutpoint gives the likelihood ratio (LR) for that value of the test. In general, the amount of work required to move the object from (2,0) to (-2,0) depends on the path taken!. In each case give the gradient and the intercept on the log(y) axis. Now we want to plot our model, along with the observed data. After 500 views plot. Sample Learning Goals Interpret r (the correlation coefficient) as data points are added, moved, or removed. This example uses a subset of the data from an experiment in which nitrogen oxide emissions from a single cylinder engine are measured for various combinations of fuel and equivalence ratio (Brinkman; 1981 ). Hence, r'(t)=<-2sin(t),cos(t)>. Although not nearly as popular as ROCR and pROC, PRROC seems to be making a bit of a comeback lately. How to make a scatter plot in R with Regression Line (ggplot2) - Duration: 7:39. This chapter of the tutorial will give a brief introduction to some of the tools in seaborn for examining univariate and bivariate distributions. I'm trying for the first time ever R Scripting with ggplot. I took out the freq and col options to get a histogram plotted, but the curve function plots a horizontal line at approximately 0. # Plots a line graph for all columns in data frame 'y'. Include 95% CI in graph: Allows to plot the 95% confidence interval for the survival curves. The expression is written using the format for writing mathematical operations in R Two number parameters called from and to that represent the first and the last points of the range of independent parameter x. Two crossed lines that form an 'X'. Plots, Graphs, and Curves in the World of Linux. Density plot line colors can be automatically controlled by the levels of sex: # Change density plot. Thus in the simplest approximation the characteristic curves of a NPN are a set of flat, evenly spaced, lines: Each (flat) curve shows that I C doesn't change with changing V CE. Please feel free to comment/suggest if I missed. xts time series objects which inherit from zoo’s objects for ordered time series objects. Adding Points, Lines, and Legends to Existing Plots Once you have created a plot, you can add points, lines, text, or a legend. Ask the class to help you create a plot line diagram using the short story “Total Urbanization” which the students have read the week before. (Click on the green letters for the solutions). If you dont want a line graph, you can just change the enumerator SeriesChartType. Plus the basic distribution plots aren't exactly well-used as it is. The R package survival fits and plots survival curves using R base graphs. The value of need not be between and. The second calling sequence uses operator form. The variable that might be considered an explanatory variable is plotted on the x axis, and the response variable is plotted on the y axis. The slope of the tangent line at a cutpoint gives the likelihood ratio (LR) for that value of the test. They are in constant motion, so fixing an exact position of any planet is valid only for a moment. The comments before each code line explains the function called for the plot. When you are finished, you will be able to create an epidemic curve, or “epi curve. 2: I can overlay a smoothed line on top of the KM step-plot by adding: + geom_line() to. Any point on our budget line (brown) represents a point at which we will spend our entire budget. 3-1) on the same graph. library ( sm ) sm. Hurricane model plots Hurricane Model Plots. Scatter plot, Correlation, and Line of Best Fit Exam : Interpret Linear Models ANSWER KEY Mrs Math 1. ) The below plot compares the percentile plot (red) to the cumulative fraction. The budget line intersects with the point (2,2) along the pink indifference curve indicating that we can hire Chris for 2 hours and Sammy for 2 hours and spend the full $40 budget, if we so choose. Include 95% CI in graph: Allows to plot the 95% confidence interval for the survival curves. Your code doesn't work. library ( sm ) sm. I realize this is a stupid question, and I have honestly tried to find the answer online, but nothing I have tried has worked. It is possible to have the estimated Y value for each step of the X axis using the predict() function, and plot it with line(). This is referred as normal distribution in statistics. Curves are defined as data frames with x and y columns providing cartesian coordinates for the lines. As we usually use decimals in probabilities you can also say that the area is equal to 1 (because 100% as a decimal is 1). You can also add a line for the mean using the function geom_vline. The most basic plotting skill it to be able to plot x,y points. The perceived loudness at 1000 Hz is the reference point for defining the equal loudness curve through that point, so the numerical value of phons and dB is always the same at 1000 Hz. If, by contrast, the health sector variable takes higher (lower) values amongst poorer people, the concentration curve will lie above (below) the line of equality. Generally, the higher the order, the tighter the curve fits your existing data, but the more unpredictable your. Additionally, density plots are especially useful for comparison of distributions. DatPlot is intuitive to use, allowing you to spend more time analyzing your data and less time struggling with your plotting software for the desired report plot look. I know there are many methods to fit a smooth curve but I'm not sure which one would be most appropriate for this type of curve and how you would write it in R. Plotting a function is often helpful to better understand what's going on. Can anybody please help with this? I know I need to use "nls" but I cannot seem to do it. Online Scatter Plot Generator. The log=T option does extra work to avoid log(0), and to try to create a pleasing result. In the above plot x vs. Contents 1 Smoothing by Directly Penalizing Curve Flexibility 1. ggplot2 improves the graphics drawn with R. In this section we will give a quick review of some important topics about functions of several variables. Use either the Java Scatter Plot program or another graphing utility to plot the data points listed in Example 3 and find the least squares regression line. Usually it follows a plot(x, y) command that produces a graph. where R is the region bounded by the cardioid 4) Compute the area of the region bounded by the two curves x^2 - y^2 = 1 and y = x^2 - 3*x + 1. , but without plotting the points. quantile plots the ordered values of varname against the quantiles of a uniform distribution. Syntax R Line plot. In each case give the gradient and the intercept on the log(y) axis. These points are ordered in one of their coordinate (usually the x-coordinate) value. Despite two large values which may be outliers in the data, the residuals do not seem to deviate. If, by contrast, the health sector variable takes higher (lower) values amongst poorer people, the concentration curve will lie above (below) the line of equality. points() is a generic function to draw a sequence of points at the specified coordinates. A variety of methods for drawing labels are implemented, ranging from positioning using the mouse to automatic labeling to automatic placement of key symbols with manual placement of key legends to automatic placement of legends. For example, I often compare the levels of different risk factors (i. abline() adds a line to the current graphic. The Algorithm. The ROCR package provides the prediction() and performance() functions which generate the data required for plotting the ROC curve, given a set of predictions and actual (true) values. When the slope is positive, the line is an increasing function, that is, as x increases in value the value of y also increases: this in known as positive linear relationship (see Figure 3. Its I vs, V characteristic curve is similar to ordinary diode. Creating plots in R using ggplot2 - part 7: histograms written February 28, 2016 in r , ggplot2 , r graphing tutorials This is the seventh tutorial in a series on using ggplot2 I am creating with Mauricio Vargas Sepúlveda. Adding LOESS Lines to Plots in R. ranger might be the surprise in my very short list of survival packages. surv_summary(): Summary of a survival curve. A plot of the vector field and the curve is shown above. Play with the Properties of the equation of a straight line. Student: OK, now I know that in order to find out if a line is a good fit for a set of data I can look at the residual plot and if the residuals are a pattern then the line is not a good fit. ROC curve example with logistic regression for binary classifcation in R. An example of putting multiple curves on a plot Here are the MATLAB commands to create a symbol plot with the data generated by adding noise to a known function. The Standard Normal curve, shown here, has mean 0 and standard deviation 1. The second statemen. Ok, I figured out the issue. Enhanced Solution. A pattern in the residuals plot is an indication of the mathematical relationship not truly fitting the data, even if the SSE is small. Data visualization in R: Add smooth curve and shaded area to a plot Veröffentlicht am Juni 26, 2016 von oliverfunke Within this article I want to show you an easy way to add a smooth curve to your plot, create an area around this curve and fill the area with a transparent color. In the R script shown below, we plot the curves of three data sets (x,y1),(x,y2) and (x,y3) on the same plot. 4 Combined Line and Bar Plot. Velocity (v) is vertical. Six successive plots following the call will be filled along columns. Fo r example, you cannot generate a fit at the command line and then import that fit into the Curve Fitting Tool. In the chart, select a data series. calculates the least-squares line of best fit for given data points, a plot those points, and a plot of the points together with the best-fitting curve. However I've encountered a small roadblock. Plotting the Kaplan-Meier curves in R is not too difficult (in my opinion). The value r 2 is a statistical measure of the linearity of the curve fit and is called the correlation coefficient. You'll now use the ggplot2 package to turn your results into a visualization of the percentage of "yes" votes over time. The second calling sequence uses operator form. The area under the density curve is equal to 100 percent of all probabilities. This post introduces the metrics required to plot ROC/PR curves, how to compute these metrics and plot the curves using R. On the same plot you will see the graphic representation of the linear regression equation. This is known as the line of equality. As we've already seen, it is often times very difficult to graph surfaces in $\mathbb{R}^3$ on a flat surface. A line chart is a graph that connects a series of points by drawing line segments between them. The Area Under Curve (AUC) metric measures the performance of a binary classification. First attempt at rarefaction curves with custom colours. Plot the subgroup averages on the X chart and connect consecutive points with a straight line. For example, to change the label style, the box type, the color, and the plot character, try the following:. Level 2 in the construction of the Koch Curve. calculates the least-squares line of best fit for given data points, a plot those points, and a plot of the points together with the best-fitting curve. To start off let’s see how to plot a sine wave in R. The line graph is popular as a visual display to trace how the value of a variable changes through time. or use the plot function as. This page will help you to do that. Color or monochrome output. , you don't have to pay for it). But how to draw curves using ggplot2? That's a little bit more complicated by can still be accomplished by 1-2 lines. Some people try to use curve fitting to find which of thousands of functions fit their data. Change the line color to a shade of blue-green using an RGB color value. Below the for there are 4 lines of code where I set up how I’d like my graphs to be like. So basically then I plot the fitted line from the mixed model in the Observed values but the only thing I managed to do yet is get a graph of predicted and absolute values (in one or separate graphs) but the line is not really the line from the equation I get from model applied above:. Each member of the dataset gets plotted as a point whose x-y coordinates relates to its values for the two variables. For this, we will use the economics data set provided by the R TIP. The normal probability plot of the residuals should approximately follow a straight line. What is 'Yield Curve'. ” You can move through this lesson by using the NEXT and BACK icons below. Gain additional perspective by studying polar plots, parametric plots, contour plots, region plots and many other types of visualizations of the. Working with graphics in RStudio. If you absolutely must have an equation for the trend line of the iso-efficiency curve, you will need to break it into two pieces at the minimum flow point, and correlate each one separately. The comments before each code line explains the function called for the plot. Data derived from ToothGrowth data sets are used. Plot level curves (contour lines) of the matrix z, using the contour matrix c computed by contourc from the same arguments; see the latter for their interpretation. where R is the region bounded by the closed curve 3) Evaluate. A detailed documentation of the algorithm and more program examples are availble in PDF: Bresenham. To accomplish this, we just switch geom_point() for geom_line() and add a linear smooth by specifying method = "lm" to stat_smooth(). How to create candlestick charts in R. In this article we will show you, How to Create a ggplot line plot, Format its colors, add points to line plot with example. Here is a v vs. We can also use curve (as we would line or points) to draw points rather than a line: curve(x^2, type = "p") We can also specify to and from arguments to. This is referred as normal distribution in statistics. In these cases, linear regression will fit a straight line to the data but the graph will appear curved since an axis (or both axes) are not linear. Also, curve can take an expression as input, but plot needs a function as input to dispatch to plot. However, this failure time may not be observed within the study time period, producing the so-called censored observations. 578 cos ∆ 2 - 5729. The article contains eight examples for the plotting of lines.