[R] using tapply() with the quantile function?

Hi: Summary: I am trying to determine the 90th percentile of ambulance response times for groups of data. Background: A fire chief would like to look at emergency response times at the 90th percentile for 1 kilometer grids in Cape Coral, Florida. I have mapped out ambulance response times on

Re: [R] using tapply() with the quantile function?

1) tapply will work for quantile, but the syntax was a little off: try this tapply(Cape $ ResponseTime, Cape $ Grid_ID, quantile, c(0.05, 0.95)) The fourth argument is additional parameters passed to the function FUN which here is quantile. You could also do this tapply(Cape $ ResponseTime, Cape

Re: [R] using tapply() with the quantile function?

There's a slight variant that might be even more helpful if you need to line the data up with how you started: ave(). I'll let you work out the details, but the key difference is that it returns a vector that has the 90th percentile for each group, each time that group appears, instead of the

Re: [R] using tapply() with the quantile function?

David: You need to re-read ?tapply _carefully_.  Note that: FUN the function to be applied, or NULL. In the case of functions like +, %*%, etc., the function name must be backquoted or quoted. Now note that in tapply(whatever, byfactor, mean), mean _is_ a function. However in tapply