Check the columns of the datasets

check_cols.R

### check whether the column names of 3 datasets match up 
columns = sapply(series_data_, colnames)

### !!! The code below certainly works for datasets with small numbers of columns, 
### However, what if we have 1000 columns to do pair-wise checking, 
### or additional columns being added to the datasource? 
all(columns[, 1] == columns[, 2])
all(columns[, 2] == columns[, 3])
all(columns[, 1] == columns[, 3])

###========== the DRY principle: DON'T REPEAT YOURSELF
### let's do it in a smarter way :)
comb_cols = combn(seq(ncol(columns)), 2)

check_colnames <- function(x, y){
  identical(columns[, x], columns[, y])
}

colnames_match = sapply(seq(ncol(comb_cols)), function(i) check_colnames(x = comb_cols[1, i], y = comb_cols[2, i]))
stopifnot(all(colnames_match))