Under the WGCNA tutorial relating modules to traits, I got an error for the R script below due to the different between the tutorial (left) and my datTraits (right) as shown in the picture below. May I know how do I correlate the modules to traits if my sample is categorical tissue sample (right hand of the image) and not variable numeric numbers as the tutorials (left hand of the image)?

```{r}

moduleTraitCor = cor(MEs, datTraits, use = "p");

Warning message: In storage.mode(y) <- "double" : NAs introduced by coercion