Count number of rows matching a criteria

Question

I am looking for a command in R which is equivalent of this SQL statement. I want this to be a very simple basic solution without using complex functions OR dplyr type of pa

Answer 1

1. mydata$sCode is a vector, it's why nrow output is NULL.
2. mydata[mydata$sCode == 'CA',] returns data.frame where sCode == 'CA'. sCode includes character. That's why sum gives you the error.

3. subset(mydata, sCode='CA', select=c(sCode)), you should use sCode=='CA' instead sCode='CA'. Then subset returns you vector where sCode equals CA, so you should use

   length(subset(na.omit(mydata), sCode='CA', select=c(sCode)))

Or you can try this: sum(na.omit(mydata$sCode) == "CA")