DF <- data.frame(A=1,B=2,C=3,D=4,E=5,F=6,G=7,H=8,I=9,J=10,K=11,L=12)
DF
#> A B C D E F G H I J K L
#> 1 1 2 3 4 5 6 7 8 9 10 11 12
NMs <- c("P18", "P18","P19", "P19", "P20", "P20", "P21", "P21",
"P22", "P22", "P23", "P23")
NMs <- paste(NMs,c("corr","p_value"),sep="_")
colnames(DF) <- NMs
DF
#> P18_corr P18_p_value P19_corr P19_p_value P20_corr P20_p_value P21_corr
#> 1 1 2 3 4 5 6 7
#> P21_p_value P22_corr P22_p_value P23_corr P23_p_value
#> 1 8 9 10 11 12
Created on 2022-02-05 by the reprex package (v2.0.1)