Better behavior for scientific and comma.

Fixes #7

NEWS

@@ -8,4 +8,8 @@
 * Simplified algorithm for `discrete_range` that is robust to
   `stringsAsFactors` global option.  Now, the order of a factor will only be 
   preserved if the full factor is the first object seen, and all subsequent 
-  inputs are subsets of the levels of the original factor.
+  inputs are subsets of the levels of the original factor.
+
+* `scientific` ensures output is always in scientific format and off the
+  specified number of significant digits. `comma` ensures output is never in
+  scientific format. (Fixes #7)

R/formatter.r

@@ -15,7 +15,7 @@ comma_format <- function(...) {
 #' @export
 #' @rdname comma_format
 comma <- function(x, ...) {
-  str_trim(formatC(x, ..., big.mark = ","))
+  format(x, ..., big.mark = ",", scientific = FALSE, trim = TRUE)
 }
 
 #' Currency formatter: round to nearest cent and display dollar sign.
@@ -80,7 +80,8 @@ scientific_format <- function(digits = 3, ...) {
 #' @export
 #' @rdname scientific_format
 scientific <- function(x, digits = 3, ...) {
-  format(x, trim = TRUE, digits = digits, ...)
+  x <- signif(x, digits)
+  format(x, trim = TRUE, scientific = TRUE, ...)
 }
 
 #' Parse a text label to produce expressions for plotmath.

inst/tests/test-formatter.r

@@ -0,0 +1,29 @@
+context("Formatters")
+
+test_that("comma format always adds commas", {
+  expect_equal(comma(1e3), "1,000")
+  expect_equal(comma(1e6), "1,000,000")
+  expect_equal(comma(1e9), "1,000,000,000")
+})
+
+test_that("scientific format shows specific sig figs", {
+  expect_equal(scientific(123456, digits = 1), "1e+05")
+  expect_equal(scientific(123456, digits = 2), "1.2e+05")
+  expect_equal(scientific(123456, digits = 3), "1.23e+05")
+
+  expect_equal(scientific(0.123456, digits = 1), "1e-01")
+  expect_equal(scientific(0.123456, digits = 2), "1.2e-01")
+  expect_equal(scientific(0.123456, digits = 3), "1.23e-01")
+})
+
+
+test_that("formatters don't add extra spaces", {
+  has_space <- function(x) any(grepl("\\s", x))
+  x <- 10 ^ c(-1, 0, 1, 3, 6, 9)
+
+  expect_false(has_space(comma(x)))
+  expect_false(has_space(dollar(x)))
+  expect_false(has_space(percent(x)))
+  expect_false(has_space(percent(x)))
+  expect_false(has_space(scientific(x)))  
+})