Hello everyone. I am new here. I am working on a project to identify differentially expressed gene of uterine cancer using TCGA and GTEX data. I have downloaded zip file of TCGA Gtex Expected Count Data, extracted the .txt file and saved it as zz_gencode.v23.annotation.csv file. However, I am not able to open the csv file and I am getting error.

Here is my code:

ExprSubsetBySamp = fread("TcgaTargetGtex_gene_expected_count.gz",
                         select = filterExpr)
probemap = fread("zz_gencode.v23.annotation.csv", select = c(1, 2));
exprALL = merge(probemap, ExprSubsetBySamp, by.x = "id", by.y = "sample");
Error: Elements listed in `by.x` must be valid column names in x.

Thank you so much.