fix(GUI): automatically rename the date column of ObsDF

Refs #38

R/ShinyGR.R

@@ -21,6 +21,7 @@ ShinyGR <- function(ObsDF = NULL, DatesR = NULL, Precip = NULL, PotEvap = NULL,
     }
   }
   if (is.data.frame(ObsDF)) {
+    colnames(ObsDF)[1L] <- "DatesR"
     ObsDF <- list(ObsDF)
   }