[R] Working With Variables Having Different Lengths

[Rich Shepard]

   Because of regulatory requirement changes over several decades and weather
conditions preventing site access the variables in my data set have
different lengths. I'd like guidance on how to perform linear regressions
and other models with these variables.

   For example, there are 2206 rows for the parameter "TDS" but only 1191
rows for the parameter "Cond." Such discrepancies are common in these data.

   Is there a reference I can read to learn how to analyze such data?

Rich