There is a package called corrplot for R and it can handle many variables well.

Its easy to handle and has a lot of options.

Good intro:

https://cran.r-project.org/web/packages/corrplot/vignettes/corrplot-intro.html

For example:

### Loading package 
install.packages("corrplot")
library(corrplot)
### Make some data - only numeric 
data_example <- matrix(rnorm(30*1000), ncol=30)
### Calculate correlation with base R 
M <- cor(data_example)
M
### Create plot with corrplot
corrplot(M, method = 'square', order = 'FPC', type = 'lower', diag = FALSE)