Looping over dataframe to create scatterplots - r

Question

Data frame
x <- data.frame(id = c("A","B","C"), x_predictor = c(5,6,7), x_depended = c(5.5, 6.5, 7.5), y_predictor=c(2,3,2), y_depended=c(3,3,2), z_predictor=c(12,10,12), z_depended=c(14,11,13))
> x
id x_predictor x_depended y_predictor y_depended z_predictor z_depended
1 A 5 5.5 2 3 12 14
2 B 6 6.5 3 3 10 11
3 C 7 7.5 2 2 12 13
I would like to create a scatterplot for each level on ID and for each pair depended and predictor.
I have created a for loop where I loop over unique levels in ID, but how can I loop over pairs of depended and predictor?
uni <- unique(x$id)
for (p in uni){
print(ggplot(x[x$id==p], aes(y = x_depended,x = x_predictor))+geom_point()
}
I would like to plot depended vs predictor. Depended will always be in following column to its predictor.

Answer 1

This code will plot three different scatter plots where each plot will contain the different columns that you have in your data frame.
require(ggplot2)
x_plots <- list()
uni <- unique(x$id)
uni_counter <- 0
i <- 0
for (colnum in seq(2, 6, 2)) {
x_col <- names(x)[colnum]
y_col <- names(x)[colnum + 1]
# Retrieve the current uni.
curr_uni <- uni[uni_counter]
# Increment our counters
uni_counter <- uni_counter + 1
i <- i + 1
# Create the ggplot command,
# the command is created dynamically so that we can iterate through
# different columns in our data frame.
ggplot_cmd <- paste0("x_plots[[i]] <- ggplot(x[x$id == curr_uni], aes(y = ", y_col, ", x = ", y_col, "))+geom_point()")
# Evaluate each plot.
eval(parse(text = ggplot_cmd))
}
You can than load the multiplot() function posted here to draw all the generated plots in one figure using:
multiplot(plotlist = x_plots)
Hope this helps.