Plotting list of functions using for loop in R

Question

How can you plot a list of functions in one graph using a for loop in R? The following code does the trick, but requires a separate call of plot for the first function outside of the for loop, which is very clunky. Is there a way to handle all the plotting inside the for loop without creating multiple plots?

vec <- 1:10
funcs <- lapply(vec, function(base){function(exponent){base^exponent}})

x_vals <- seq(0, 10, length.out=100)
plot(x_vals, funcs[[1]](x_vals), type="l", ylim=c(0,100))
for (i in 2:length(vec)) {
  lines(x_vals, funcs[[i]](x_vals))
}

You still need the first function to define the x and y limits. Base R plots don't update the view region when you add additional elements. Would you rather use something like ggplot instead of base R? — MrFlick
– MrFlick, Commented Jan 31, 2023 at 21:36
@MrFlick Thanks! Maybe I ought to switch to ggplot, I just like keeping imports to a minimum, but only so much can be done. I think I just found a work-around, I'll post it as an answer below. — TimH
– TimH, Commented Jan 31, 2023 at 21:39

Robert Hacken · Accepted Answer · 2023-01-31 22:04:30Z

2

You can also do the computations first and plotting after, like this:

vec <- 1:10
funcs <- lapply(vec, function(base) function(exponent){base^exponent})

x_vals <- seq(0, 10, length.out=100)
y_vals <- sapply(funcs, \(f) f(x_vals))
plot(1, xlim=range(x_vals), ylim=range(y_vals), type='n', log='y', 
     xlab='x', ylab='y')
apply(y_vals, 2, lines, x=x_vals)

This way you know the range of your y values before initiating the plot and can set the y axis limits accordingly (if you would want that). Note that I chose to use logarithmic y axis here.

answered Jan 31, 2023 at 22:04

Robert Hacken

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TimH · Accepted Answer · 2023-01-31 22:32:01Z

0

Based on MrFlick's comment, it looks like something like this would be one way to do what I'm looking for, but is still not great.

vec <- 1:10
funcs <- lapply(vec, function(base){function(exponent){base^exponent}})

x_vals <- seq(0, 10, length.out=100)
plot(NULL, xlim=c(0,10), ylim=c(0,100))
for (i in 1:length(vec)) {
  lines(x_vals, funcs[[i]](x_vals))
}

edited Jan 31, 2023 at 22:32

answered Jan 31, 2023 at 21:41

TimH

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