Here is a repository called The Road to Progress that I created to show how to got from a for loop to lapply/sapply. Learn about vectorized functions designed to replace for loops: lapply, sapply, and apply. In other words only make 8 calls to slow_function but return 16 rows of results. You are an R user but havent used vectorized functions yet. What I don't know is the magic incantation to get the result I want! I've tried initializing results to be matrix() or list() instead, with identical output.ĪSIDE: Why do I want to use a for loop? I actually want to do two calculations per pass of the sapply loop. R Introduction R Operators R Vector R List R Matrix R Data Frame R Factor R IfElse R switch() Function R While Loop R For Loop R Repeat Loop R Functions R Apply Functions Read/Write CSV Files Read/Write Excel Files Create a basic plot R Bar Plot R Scatter Plot R Box-whisker Plot R Histogram R Pie Chart R Quantile-Quantile (QQ) Plot R Bar. Number of items to replace is not a multiple of replacement length Then I get 8 warning messages like: 1: In results = list(a = a, up = b, down = b, level = b) : excel Create a loop until all cells have been used by script Apexcel Leave a comment Questions: I don’t really know how to program but I have compiled a few scripts to achieve nearly what I want, but I have failed at the last step. When I turn it into a for loop: results=vector() (That is good, though incidentally I actually want it transposed, with values of n as the rows, and a, up, down, level as the columns.

Indeed, in gengrow(), at each iteration of the loop, we reallocate a new matrix with one more column, which takes time. Here is a simplification of the sapply version of my code: slow_function=function(n) c(n*n, 0, (-n)^n, -1, +1) Wow, sapply() is so much faster than loops Don’t get this wrong, sapply() or lapply() is nothing but a loop internally, so sapply() shouldn’t be any faster than a loop.Here, the problem is not with the loop, but what we do inside this loop. mapply str(mapply) Output: function (FUN,, MoreArgs NULL, SIMPLIFY TRUE, USE.NAMES TRUE) FUN is a function to apply contains R objects to apply over MoreArgs is a list of other arguments to FUN. To get the list of arguments it takes just type str(mapply). (See further down for why, if interested.) Get the help file by typing mapply in your R console. apply lapply rapply sapply functions in R, lapply(): lapply function is. There are some exception as for example Hadley Wickham points out in his Advance R book.I want to replace the behaviour of sapply with a for loop. Nested For Loop in R, Nested for loops are used to manipulate a matrix by making.

It is often said that one should prefer lapply over for loops.

Sapply for loop in r