[FIXED] How make a gradient plot in R from a matrix data stored in a .csv file?

Issue

I have a xyz matrix stored in a .csv file that, for example, looks like the following:

   1  2  3  4
1  1  1 -1  1
2 -1  1  1  1
3  1 -1  1 -1
4  1  1 -1  1

where the rows are x, columns are y and entries are z. I could store this matrix in a dataframe.

I want to create a heatmap of this matrix, where the entries would just be two colors, depending on 1 or -1. The plot would look like the following for an 18 X 18 matrix (done by a colleague in matlab probably):

where, say, yellow is for 1 and blue for -1.

How can I do this in R?

Solution

Use geom_tile(). First you need to flatten your dataframe using melt from the package reshape2.

library(reshape2)
flat_df <- melt(t(df), value.name = "Value")
ggplot(data=flat_df,aes(y=y,x=x))+geom_tile(aes(fill=Value))+scale_y_reverse()

Answered By - Soccerama

Answer Checked By - David Marino (PHPFixing Volunteer)