Plot Cumulative Distribution Function in R
In this article, we will discuss how to plot a cumulative distribution function (CDF) in the R programming Language.
The cumulative distribution function (CDF) of a random variable evaluated at x, is the probability that x will take a value less than or equal to x. To calculate the cumulative distribution function in the R Language, we use the ecdf() function. The ecdf() function in R Language is used to compute and plot the value of the Empirical Cumulative Distribution Function of a numeric vector. The ecdf() function takes the data vector as an argument and returns the CDF data.
Syntax: ecdf( data_vector )
- data_vector: determines the vector that contains data for CDF calculation.
Plot cumulative distribution function in base R
To plot a CDF function in base R, we first calculate the CDF by using the ecdf() function. Then we use the plot() function to plot the CDF plot in the R Language. The plot function takes the result of the ecdf() function as an argument to plot the CDF plot.
Syntax: plot( CDF )
- CDF: determines the cumulative distribution function calculated using the ecdf() function.
Example 1: Cumulative distribution function in base R
Here, is an example of a basic Cumulative Distribution Function Plot in the R Language.
Example 2: Cumulative distribution function in base R using iris dataset
Plot CDF of Known Distribution
To plot the cumulative distribution function of a standard distribution in a specific known range, we use the curve() function in the R Language. The curve() function draws a curve corresponding to a function over the interval. It takes an expression as an argument that in this case will be pnorm along with the limits from and to and returns a Normal CDF Plot.
Syntax: curve( expression, from, to )
- expression: determines the expression function for CDF calculation.
- from: determines the lower limit of data.
- to: determines the upper limit of data.
Here, is an example of a normal CDF plot.
Plot CDF of Known Distribution using ggplot2 Package
To draw the same plot in the ggplot2 package library, we use the stat_function() function. The stat_function takes the expression function as a fun argument and converts the curve according to that expression in a basic ggplot2 plot.
Syntax: plot + stat_function( fun )
- fun: determines the function for the shape of the plot.
Here, is an example of a normal CDF plot using ggplot2.