Question

I thought the summary function in R could take character variables given the file it points to is numeric. bbb is giving me good results but the summary of aaa is giving me problems.

# Descriptives For Machine.x
for (n in 1:3500){
   machine_name = paste("machine.wt$Machine.", n, sep="")
   aaa = summary (paste("machine.wt$Machine.", n, sep=""))
   bbb = summary (machine.wt$Machine.1)
}

Error in x - mx : non-numeric argument to binary operator
In addition: Warning messages:
1: In mean.default(x, na.rm = na.rm) :
  argument is not numeric or logical: returning NA
2: In var(x, na.rm = na.rm) : NAs introduced by coercion
3: In mean.default(x, na.rm = na.rm, trim = trim) :
  argument is not numeric or logical: returning NA
4: In var(x, na.rm = na.rm) : NAs introduced by coercion
5: In mean.default(x) : argument is not numeric or logical: returning NA

My data is very simple:

Obs.1   Machine.1   Obs.1   Machine.2   Obs.2   Machine.3   Obs.3   Machine.4
1   302.3   1   302.8   1   315.1   1   300.9
2   295.3   2   314.3   2   306.7   2   317.5
3   301.4   3   308.4   3   309.0   3   304.3
4   318.2   4   295.2   4   321.3   4   293.2
5   320.4   5   313.5   5   326.4   5   308.0

Answer 1

How about using subset and grepl to avoid the loop altogether?

summary(subset(machine.wt,select=grepl("^Machine",names(machine.wt))))