Soroosh Soroosh - 3 months ago 15
R Question

Change the title of the second group in ggplot2 in R

Assume I have a function_3d with three parameters x, y, z . Assume the function is defined as the following:

function_3d <- function(x, y, z) {
return(x + y * 10 + z * 100)
}


I am plotting this function using ggplot2 for x in seq(0, 10, 1) while y has a value from c(1, 3, 5, 7) and z has a value from c(2, 4, 6).

Here is my approach:

require('ggplot2')
require('dplyr')

function_3d <- function(x, y, z) {
return(x + y * 10 + z * 100)
}


x_vec <- seq(0, 10, 1)
y_vec <- c(1, 3, 5, 7)
z_vec <- c(2, 4, 6)

allframes <-
lapply(z_vec, function(inp.z.val) {
(lapply(y_vec, function(inp.y.val)
{
data.frame(
x = x_vec,
y = function_3d(x = x_vec,
y = inp.y.val,
z = inp.z.val),
group_y = inp.y.val,
group_z = inp.z.val
)
}))
})

# Bind all the frames
# Note: we can use dply::bind_rows instead of rbind
df.out <- do.call(rbind, do.call(rbind, allframes))

ggplot(df.out,
aes(
x = x,
y = y,
shape = factor(group_y),
colour = factor(group_z),
group = interaction(group_y, group_z)
)) +
geom_line(aes(linetype=factor(group_y)), alpha = .9, size = 1) +
scale_x_continuous(name = "X Label") +
scale_y_continuous(name = "Y Label") +
ggtitle("Plot Title") +
scale_colour_brewer(palette = "Set1") +

labs(aes(colour = "Label of each plot z")) +
theme(legend.key.width=unit(3, "line"))


And the result is:

Plot of function_3d

Now I have two questions:

1) How can I change the label of y group ( I mean change factor(group_y) text) ?

2) Is there a better way to create this plot?

AEF AEF
Answer

You can drastically simplify the creation of your data.frame by using expand.grid which is made exactly for this situation.

I don't see why you need the interaction of group_y, group_z in your ggplot?

What I would have done is the following:

library(ggplot2)
function_3d <- function(x, y, z) {
    return(x + y * 10 + z * 100)
}

df.out <- expand.grid(x = seq(0, 10, 1),
                      group_y = c(1, 3, 5, 7),
                      group_z = c(2, 4, 6))

df.out$y <- function_3d(df.out$x, df.out$group_y, df.out$group_z)

ggplot(df.out, aes(x = x, y = y)) +
    geom_line(aes(color = factor(group_z), linetype = factor(group_y))) +
    xlab("Test label x") +
    ylab("Test label y") +
    ggtitle("testtitle") +
    scale_color_brewer(palette = "Set1", name = "color label") +
    scale_linetype_discrete(name = "linetype label")
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