r - error: replacement has 1 row, data has 0 -

corr <- function(directory, threshold = 0) {   setwd("c:/users/hp1/desktop")   files_full <- list.files(directory,full.names = true)   cr <- data.frame()   j = 1   for(i in 1:332)   {     y <- read.csv(files_full[i])     z <- y[complete.cases(y),]      if (nrow(z) > threshold){       cr[j] <- cor(z[,'sulfate'], z[,'nitrate'], method = "pearson")        j = j+1       }       }   cr    } 

it's showing following error: error in [<-.data.frame(*tmp*, j, value = -0.222552560758546) : replacement has 1 row, data has 0 expecting j increments, values added cr dtaframe. not happening. please suggest necessary changes

you try this. if provide reproducible example can show how clean result. sapply try simplify result, can stop specifying simplify = false , remove unwanted list elements.

setwd("c:/users/hp1/desktop") # use outside function  corr <- function(directory, threshold = 0) {   files_full <- list.files(directory, full.names = true)    sapply(files_full, fun = function(x) {     y <- read.csv(x)     z <- y[complete.cases(y),]      if (nrow(z) > threshold){       out <- cor(z[,'sulfate'], z[,'nitrate'], method = "pearson")     } else {       return(na) # or other way want handle result     }   }) }