'modify'-> 'alter'

Author: gdemin

DESCRIPTION

@@ -1,7 +1,7 @@
 Package: comprehenr
 Type: Package
 Title: List Comprehensions
-Version: 0.6.0
+Version: 0.6.5
 Maintainer: Gregory Demin <gdemin@gmail.com>
 Authors@R: person("Gregory", "Demin", email = "gdemin@gmail.com",
          role = c("aut", "cre"))

NAMESPACE

@@ -1,9 +1,9 @@
 # Generated by roxygen2: do not edit by hand
 
+export(alter)
 export(enumerate)
 export(lag_list)
 export(mark)
-export(modify)
 export(numerate)
 export(to_list)
 export(to_vec)

NEWS

@@ -1,6 +1,6 @@
 0.6.5 (09.04.2019)
 ================
-* add for lists/data.frames modification
+* add 'alter' function for conditional lists/data.frames modification
 
 0.6.0 (18.03.2019)
 ================

R/to_list.R

@@ -1,12 +1,18 @@
 #' List comprehensions for R
 #'
-#' \code{to_list} converts usual R loops expressions to list producers.
+#' \itemize{\item{\code{to_list}}{ converts usual R loops expressions to list producers.
 #' Expression should be started with \code{for} ,  \code{while} or
 #' \code{repeat}. You can iterate over multiple lists if you provide several
-#' loop variables in backticks. See examples.
+#' loop variables in backticks. See examples.}
+#' \item{\code{to_vec}}{ is the same as \code{to_list} but return vector. See examples.}
+#' \item{\code{alter}}{ return the same type as its argument but with modified
+#' elements. It is useful for altering existing data.frames or lists. See
+#' examples.}
+#' }
 #' @param expr expression which starts with \code{for} ,  \code{while} or \code{repeat}.
 #' @param recursive	logical. Should unlisting be applied to list components of result? See \link[base]{unlist} for details.
 #' @param use.names logical. Should names be preserved? See \link[base]{unlist} for details.
+#' @param data data.frame/list/vector which we want to alter
 #' @return list for \code{to_list} and vector for \code{to_vec}
 #' @export
 #'
@@ -33,6 +39,31 @@
 #' rand_sequence = runif(20)
 #' # gives only locally increasing values
 #' to_vec(for(`i, j` in lag_list(rand_sequence)) if(j>i) j)
+#'
+#' # 'alter' examples
+#' data(iris)
+#' # scale numeric variables
+#' res = alter(for(i in iris) if(is.numeric(i)) scale(i))
+#' str(res)
+#'
+#' # convert factors to characters
+#' res = alter(for(i in iris) if(is.factor(i)) as.character(i))
+#' str(res)
+#'
+#' # 'data' argument example
+#' # specify which columns to map with a numeric vector of positions:
+#' res = alter(
+#'     for(`i, value` in numerate(mtcars)) if(i %in% c(1, 4, 5)) as.character(value),
+#'     data = mtcars
+#' )
+#' str(res)
+#'
+#' # or with a vector of names:
+#' res = alter(
+#'     for(`name, value` in mark(mtcars)) if(name %in% c("cyl", "am")) as.character(value),
+#'     data = mtcars
+#' )
+#' str(res)
 to_list = function(expr){
     expr = substitute(expr)
     if(!is_loop(expr)) {
@@ -41,7 +72,7 @@ to_list = function(expr){
 
     expr = expand_loop_variables(expr)
     expr = add_assignment_to_final_loops(expr)
-    on.exit(suppressWarnings(rm(list = c(".___res", ".___counter", ".__curr"), envir = parent.frame())))
+    on.exit(suppressWarnings(rm(list = c(".___res", ".___counter", ".___curr"), envir = parent.frame())))
     eval.parent(quote(.___res <- list()))
     eval.parent(quote(.___counter <- 0)) # initial list length
     eval.parent(expr)
@@ -131,20 +162,20 @@ add_assignment_to_loop = function(expr, result_exists = FALSE){
     last_item = length(expr)
     if(result_exists){
         expr[[last_item]] = bquote({
-            .__curr = {.(expr[[last_item]])}
+            .___curr = {.(expr[[last_item]])}
             .___counter = .___counter + 1
-            if(!is.null(.__curr)){
-                .___res[[.___counter]] = .__curr
+            if(!is.null(.___curr)){
+                .___res[[.___counter]] = .___curr
             }
 
         })
     } else {
         expr[[last_item]] = bquote({
 
-            .__curr = {.(expr[[last_item]])}
-            if(!is.null(.__curr)){
+            .___curr = {.(expr[[last_item]])}
+            if(!is.null(.___curr)){
                 .___counter = .___counter + 1
-                .___res[[.___counter]] = .__curr
+                .___res[[.___counter]] = .___curr
             }
 
         })
@@ -154,12 +185,12 @@ add_assignment_to_loop = function(expr, result_exists = FALSE){
 
 #' @rdname to_list
 #' @export
-modify = function(expr, data = NULL){
+alter = function(expr, data = NULL){
     expr = substitute(expr)
     if(!is_loop(expr)) {
         stop(paste("argument should be expression with 'for', 'while' or 'repeat' but we have: ", deparse(expr, width.cutoff = 500)[1]))
     }
-    on.exit(suppressWarnings(rm(list = c(".___res", ".___counter", ".__curr"), envir = parent.frame())))
+    on.exit(suppressWarnings(rm(list = c(".___res", ".___counter", ".___curr"), envir = parent.frame())))
     if(is.null(data)) data = expr[[3]]
     eval.parent(substitute(.___res <- data))
     expr = expand_loop_variables(expr)

README.md

@@ -10,13 +10,23 @@ expressions use usual loops (`for`, `while` and `repeat`) and usual `if` as
 list producers. Syntax is very similar to Python. The difference is that
 returned value should be at the end of the loop body.
 
-```R
-# rather useless statement - squares of even numbers
-to_list(for(i in 1:10) if(i %% 2==0) i*i)
+There are three main functions:
 
-# Pythagorean triples
-to_list(for (x in 1:20) for (y in x:20) for (z in y:20) if (x^2 + y^2 == z^2) c(x, y, z))
+- `to_list` converts usual R loops expressions to list producers. Expression should be started with `for`, `while` or `repeat`. You can iterate over multiple lists if you provide several loop variables in backticks. See examples.
+- `to_vec` is the same as `to_list` but return vector. See examples.
+- `alter` return the same type as its argument but with modified elements. It is useful for altering existing data.frames or lists. See examples.
 
+Rather unpractical example - squares of even numbers:
+```R
+library(comprehenr)
+to_vec(for(i in 1:10) if(i %% 2==0) i*i)
+```
+Pythagorean triples:
+```R
+to_list(for (x in 1:20) for (y in x:20) for (z in y:20) if (x^2 + y^2 == z^2) c(x, y, z))
+```
+More examples:
+```R
 colours = c("red", "green", "yellow", "blue")
 things = c("house", "car", "tree")
 to_vec(for(x in colours) for(y in things) paste(x, y))
@@ -36,3 +46,30 @@ rand_sequence = runif(20)
 to_vec(for(`i, j` in lag_list(rand_sequence)) if(j>i) j)
 
 ```
+
+`alter` examples:
+```R
+data(iris)
+# scale numeric variables
+res = alter(for(i in iris) if(is.numeric(i)) scale(i))
+str(res)
+
+# convert factors to characters
+res = alter(for(i in iris) if(is.factor(i)) as.character(i))
+str(res)
+
+# 'data' argument example
+# specify which columns to map with a numeric vector of positions:
+res = alter(
+    for(`i, value` in numerate(mtcars)) if(i %in% c(1, 4, 5)) as.character(value),
+    data = mtcars
+)
+str(res)
+
+# or with a vector of names:
+res = alter(
+    for(`name, value` in mark(mtcars)) if(name %in% c("cyl", "am")) as.character(value),
+    data = mtcars
+)
+str(res)
+```

man/to_list.Rd

@@ -36,18 +36,18 @@ expect_equal(
 )
 expect_false(exists(".___res"))
 expect_false(exists(".___counter"))
-expect_false(exists(".__curr"))
+expect_false(exists(".___curr"))
 
 expect_error(to_list(for(i in 1:10) i*brrrr))
 expect_false(exists(".___res"))
 expect_false(exists(".___counter"))
-expect_false(exists(".__curr"))
+expect_false(exists(".___curr"))
 
 
 expect_error(to_list(1))
 expect_false(exists(".___res"))
 expect_false(exists(".___counter"))
-expect_false(exists(".__curr"))
+expect_false(exists(".___curr"))
 a = 11
 expect_error(to_list(a + 2))
 
@@ -119,20 +119,20 @@ true_res = paste(true_res[[2]], true_res[[1]])
 expect_identical(res, true_res)
 
 
-context("modify")
+context("alter")
 data(iris)
-iris2 = modify(for(i in iris) if(is.numeric(i)) scale(i))
+iris2 = alter(for(i in iris) if(is.numeric(i)) scale(i))
 res_iris = iris
 res_iris[,-5] = lapply(iris[,-5], scale)
 expect_equal(iris2, res_iris)
 
-iris2 = modify(for(`name, value` in mark(iris)) if(grepl("Width", name)) scale(value), data = iris)
+iris2 = alter(for(`name, value` in mark(iris)) if(endsWith(name, "Width")) scale(value), data = iris)
 
 res_iris = iris
 res_iris[,c("Sepal.Width", "Petal.Width")] = lapply(iris[,c("Sepal.Width", "Petal.Width")], scale)
 expect_equal(iris2, res_iris)
 
-
+expect_error(alter(1))
 # library(data.table)
 # dt_iris = as.data.table(iris)
-# dt_iris2 = modify(for(i in dt_iris) if(is.numeric(i)) scale(i))
+# dt_iris2 = alter(for(i in dt_iris) if(is.numeric(i)) scale(i))

tests/testthat/test_to_list.R

@@ -30,3 +30,28 @@ rand_sequence = runif(20)
 to_vec(for(`i, j` in lag_list(rand_sequence)) if(j>i) j)
 
 
+## ------------------------------------------------------------------------
+data(iris)
+# scale numeric variables
+res = alter(for(i in iris) if(is.numeric(i)) scale(i))
+str(res)
+
+# convert factors to characters
+res = alter(for(i in iris) if(is.factor(i)) as.character(i))
+str(res)
+
+# 'data' argument example
+# specify which columns to map with a numeric vector of positions:
+res = alter(
+    for(`i, value` in numerate(mtcars)) if(i %in% c(1, 4, 5)) as.character(value),
+    data = mtcars
+)
+str(res)
+
+# or with a vector of names:
+res = alter(
+    for(`name, value` in mark(mtcars)) if(name %in% c("cyl", "am")) as.character(value),
+    data = mtcars
+)
+str(res)
+