我想将data.frame中的变量名从"pmm_StartTimev4_E2_C19_1“更改为"pmm_StartTimev4_E2_C19”。# Current data frame:
dfbefore <- data.frame(a=c("pmm_StartTimev4_E2_C19_1","pmm_StartTimev4_E2_E2_C1","delivery_C1_C12"),b=c("pmm
at PMM.Models.PMM_DB.runStoredProcedure(String StoredProcedureName, List`1 SQLParameters) in C:\WWW\nobulus\nobulusPMM\Application\PMM\Models\PMM_DB.cs:line 104
at PMM.Models.PMM_DB.saveValidation(String PTLUniqueID\Models\PMM_DB.cs:l