Question

I’m sure there is an obvious and easy solution for this … but I’m drawing a complete blank on this one: how can I create a histogram and/or density plot using ALL data points in a data set that consists of several rows and columns?

Example data:

MYdata <- data.frame(Name = round(rnorm(12, 1000, 250)), 
                     Sample1 = rnorm(12, 10000, 2500), 
                     Sample2 = rnorm(12, 10000, 2500), 
                     Sample3 = rnorm(12, 10000, 2500), 
                     Sample4 = rnorm(12, 10000, 2500)) 

“Name” is the header of the column containing the row names. Columns Sample1 to Sample4 contain the data. hist() or geom_histogram() require an x = . But I don’t know what x is in my data set.

Thanks for your help.

Answer 1

Check out melt from the reshape2 package. Since Hadley made them both reshape2, plyr and ggplot they play very nicely together:

MYdata.melt <- melt(MYdata, id.vars='Name')

ggplot(MYdata.melt, aes(x=value, color=variable)) + geom_density()

I used geom_density() since your data is continuous, but changing to geom_histogram() is straight forward.