I have RStudio Desktop 1.4.1717 and R x64 4.1.1. I am trying to install "diamond" package in RStudio. But getting the below error:
Warning in install.packages :
package ‘diamond’ is not available for this version of R
I believe that this is suggesting that the version on CRAN is not yet compatible with your version of R, but that the in-development version on GitHub might be.
When this happens, it can often be helpful to do a websearch for "GitHub [packagename]" - and if you find a GitHub website that sounds like the right package, you can install the in-development version.
In this case (assuming that this is the right package), you can use remotes::install_github("bbuchfink/diamond") to install the development version and give it a try.
There does not appear to be a 'diamond' package available on CRAN. CRAN Packages By Name - is it possible that you are looking for the 'diamonds' dataset? This is part of the ggplot2 package.