Plot many histograms using a for loop in R

Question

I have a .csv file with data like this:

         RI    Na   Mg   Al    Si    K    Ca   Ba   Fe Type
1   1.51793 12.79 3.50 1.12 73.03 0.64  8.77 0.00 0.00  BWF
2   1.51643 12.16 3.52 1.35 72.89 0.57  8.53 0.00 0.00  VWF
3   1.51793 13.21 3.48 1.41 72.64 0.59  8.43 0.00 0.00  BWF
4   1.51299 14.40 1.74 1.54 74.55 0.00  7.59 0.00 0.00  TBL
5   1.53393 12.30 0.00 1.00 70.16 0.12 16.19 0.00 0.24 BWNF
6   1.51655 12.75 2.85 1.44 73.27 0.57  8.79 0.11 0.22 BWNF

I want to create histograms for the distribution of each of the columns. I've tried this:

data<-read.csv("glass.csv")
names<-(attributes(data)$names)
for(name in names)
{
    dev.new()
    hist(data$name)
}

But i keep getting this error: Error in hist.default(data$name) : 'x' must be numeric

I'm assuming that this error is because attributes(data)$names returns a set of strings, "RI" "Na" "Mg" "Al" "Si" "K" "Ca" "Ba" "Fe" "Type"

But I'm unable to convert them to the necessary format.

Any help is appreciated!

Answer 1

You were close. I think you were also trying to get Type at the end.

data<-read.csv("glass.csv")
# names<-(attributes(data)$names)
names<-names(data)
classes<-sapply(data,class)

for(name in names[classes == 'numeric'])
{
    dev.new()
    hist(data[,name]) # subset with [] not $
}

You could also just loop through the columns directly:

for (column in data[class=='numeric']) {
    dev.new()
    hist(column)
}

But ggplot2 is designed for multiple plots. Try it like this:

library(ggplot2)
library(reshape2)
ggplot(melt(data),aes(x=value)) + geom_histogram() + facet_wrap(~variable)