Re: [R] Efficiency of for-loop in R
Exactly what is the problem you are trying to solve? Could you provide commented, minimal, self-contained, reproducible code? A lot depends on what you are trying to do, There might be other ways, in R, than a 'for' loop to solve your problems. On Dec 27, 2007 6:44 PM, Tong Wang [EMAIL PROTECTED] wrote: Hi, I just realized that in Matlab, as long as memory is pre-allocated, doing for-loop doesn't cost more time than doing things in vector form. But it seems in R, it still cost a lot to do for-loop. Is there any improvement in R that I missed. Thanks a lot. Merry Xmas Everyone ! __ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. -- Jim Holtman Cincinnati, OH +1 513 646 9390 What is the problem you are trying to solve? __ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
Re: [R] Efficiency of for-loop in R
HI, The question is meant to be a general one, I am trying to find out if there is new development in R that I might have missed. but here's a trivial example, To compute y=sin(x) , x = 1,2,... 10 x=1:10, 1. y =sin(x) 2. for(i in 1:10) y=sin(x[i]) 1 is much faster than 2. Old Matlab also had this problem, but in new versions, 1 and 2 are mostly the same. I am just wondering if the same improvement has happened or will happen to R. Thanks . - Original Message - From: jim holtman [EMAIL PROTECTED] Date: Thursday, December 27, 2007 4:39 pm Subject: Re: [R] Efficiency of for-loop in R To: Tong Wang [EMAIL PROTECTED] Cc: R help [EMAIL PROTECTED] Exactly what is the problem you are trying to solve? Could you provide commented, minimal, self-contained, reproducible code? A lot depends on what you are trying to do, There might be other ways, in R, than a 'for' loop to solve your problems. On Dec 27, 2007 6:44 PM, Tong Wang [EMAIL PROTECTED] wrote: Hi, I just realized that in Matlab, as long as memory is pre- allocated, doing for-loop doesn't cost more time than doing things in vector form. But it seems in R, it still cost a lot to do for-loop. Is there any improvement in R that I missed. Thanks a lot. Merry Xmas Everyone ! __ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting- guide.html and provide commented, minimal, self-contained, reproducible code. -- Jim Holtman Cincinnati, OH +1 513 646 9390 What is the problem you are trying to solve? __ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
Re: [R] Efficiency of for-loop in R
I will venture a guess in that in the case of the 'for' loop, you are calling 'sin' 100,000 times incurring the cost of individual function calls at the interpreter level plus evaluating 'for' loop. In the vectorized case, you are only interpreting a single 'sin' call and then internally evaluating the 'sin' function, which is a lot faster. Also the results are different in the two cases. In case 1) you get 10 values back in 'y' and in 2) you only get the value of the last loop through the 'for' loop. system.time(for (i in 1:10) y - sin(i)) user system elapsed 0.170.000.28 str(y) num 0.0357 system.time(y - sin(1:10)) user system elapsed 0.010.000.02 str(y) num [1:10] 0.841 0.909 0.141 -0.757 -0.959 ... R is typically optimized for vector type operations. On Dec 27, 2007 8:39 PM, Tong Wang [EMAIL PROTECTED] wrote: HI, The question is meant to be a general one, I am trying to find out if there is new development in R that I might have missed. but here's a trivial example, To compute y=sin(x) , x = 1,2,... 10 x=1:10, 1. y =sin(x) 2. for(i in 1:10) y=sin(x[i]) 1 is much faster than 2. Old Matlab also had this problem, but in new versions, 1 and 2 are mostly the same. I am just wondering if the same improvement has happened or will happen to R. Thanks . - Original Message - From: jim holtman [EMAIL PROTECTED] Date: Thursday, December 27, 2007 4:39 pm Subject: Re: [R] Efficiency of for-loop in R To: Tong Wang [EMAIL PROTECTED] Cc: R help [EMAIL PROTECTED] Exactly what is the problem you are trying to solve? Could you provide commented, minimal, self-contained, reproducible code? A lot depends on what you are trying to do, There might be other ways, in R, than a 'for' loop to solve your problems. On Dec 27, 2007 6:44 PM, Tong Wang [EMAIL PROTECTED] wrote: Hi, I just realized that in Matlab, as long as memory is pre- allocated, doing for-loop doesn't cost more time than doing things in vector form. But it seems in R, it still cost a lot to do for-loop. Is there any improvement in R that I missed. Thanks a lot. Merry Xmas Everyone ! __ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting- guide.html and provide commented, minimal, self-contained, reproducible code. -- Jim Holtman Cincinnati, OH +1 513 646 9390 What is the problem you are trying to solve? -- Jim Holtman Cincinnati, OH +1 513 646 9390 What is the problem you are trying to solve? __ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
