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R / Re: Help on PCA: Error in colMeans(x, na.rm = TRUE) : 'x' must be numeric
One of your columns contains non-numeric information. This might be because your data frame (tdt) has a column specifying the treatment. Here is an example with the iris data set which has "Species" in column 5.
data("iris")
pca <- prcomp(iris) # Fails with "Error in colMeans(x, na.rm = TRUE) : 'x' must be numeric"
pca <- prcomp(iris[1:4]) # Success
Hope this helps.