[R] sapply and loop

Roger D. Peng rpeng at jhsph.edu
Sat Oct 16 14:14:52 CEST 2004

You can use system.time() to time your procedure.  There's no guarantee that 
sapply() will be faster than a for() loop, especially if you preallocate the 


Zhen Pang wrote:

> Dear all,
> I am doing 200 times simulation. For each time, I generate a matrix and 
> define some function on this matrix to get a 6 dimension vector as my 
> results.
> As the loop should be slow, I generate 200 matrice first, and save them 
> into a list named ma,
> then I define zz<-sapply(ma, myfunction)
> To my surprise, It almost costs me the same time to get my results if I 
> directly use a loop from 1 to 200. Is it common? Can I improve any further?
> Ps, how to count the exact time to finish my code?
> Thanks.
> Zhen
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide! 
> http://www.R-project.org/posting-guide.html

Roger D. Peng

More information about the R-help mailing list