Sed Regular Expression

Today I also used Sed to do some relatively complex job. So I used regular expression. However, the expression in Sed is a little bit different from normal Regexp, especially the "(". There is no need to write it as "\(", the solely "(" is OK!

#!/bin/bash
cd /Volumes/Macintosh_HD_2/Research/RData/R_Packages/TCGA_EDRN_Gene_Mining/R/
for file in *.R;
do
    echo $file
    sed -ig 's/EDRN_CNV_Gene_Eset.rda/CNV_Eset.rda/g' $file
    sed -ig 's/EDRN_TvN_ExpressionData.rda/Expression_TvN_EDRN.rda/g' $file
    sed -ig 's/EDRN_TvN_MethylationData_CC_SuhSample_BGcor.rda/Methylation_TvN_TCGA.rda/g' $file
    sed -ig 's/Expression_CellLine_Match_Ade.rda/Expression_CellLine_EDRN.rda/g' $file
    sed -ig 's/TCGA_Exp_Match.rda/Expression_TvN_TCGA.rda/g' $file
    sed -ig 's/TCGA_Meth_Match_NARM.rda/Methylation_TvN_TCGA.rda/g' $file
    sed -ig "s/load(\'\.\/Data\//data(/g" $file
    sed -ig "s/\.rda\')/)/g" $file
done