Fill contingency table based on total variable

Question

I have a list of stores and I have a product (apples). I ran a system of linear equations to get the column \'var\'; this value represents the amount of apples you will

Answer 1

I bet there are simpler ways of doing this but this one works.
The function fun outputs a result identical to the expected one.

fun <- function(DF){
  n <- nrow(DF)
  mat <- matrix(0, nrow = n, ncol = n)
  VAR <- DF[["var"]]
  neg <- which(DF[["var"]] < 0)
  for(k in neg){
    S <- 0
    Tot <- abs(DF[k, "var"])
    for(i in seq_along(VAR)){
      if(i != k){
        if(VAR[i] > 0){
          if(S + VAR[i] <= Tot){
            mat[k, i] <- VAR[i]
            S <- S + VAR[i]
            VAR[i] <- 0
          }else{
            mat[k, i] <- Tot - S
            S <- Tot
            VAR[i] <- VAR[i] - Tot + S
          }
        }
      }
    }
  }
  colnames(mat) <- paste0("ship_to_", DF[["store"]])
  cbind(DF, mat)
}

out <- fun(df)
identical(output, out)
#[1] TRUE