Add function to format as exponential

R/format.R

@@ -44,6 +44,9 @@ formatColumns = function(table, columns, template, ...) {
 #' # render vapor pressure with only two significant figures.
 #' datatable(pressure) %>% formatSignif('pressure',2)
 #'
+#' # render vapor pressure with only two 2-decimal digits in exponential format.
+#' datatable(pressure) %>% formatExp('pressure',2)
+#'
 #' # apply CSS styles to columns
 #' datatable(iris) %>%
 #'   formatStyle('Sepal.Length', fontWeight = styleInterval(5, c('bold', 'weight'))) %>%
@@ -93,6 +96,15 @@ formatSignif = function(
   formatColumns(table, columns, tplSignif, digits, interval, mark, dec.mark)
 }
 
+
+#' @export
+#' @rdname formatCurrency
+formatExp = function(
+  table, columns, digits = 2, interval = 3, mark = ',', dec.mark = getOption('OutDec')
+) {
+  formatColumns(table, columns, tplExp, digits, interval, mark, dec.mark)
+}
+
 #' @export
 #' @rdname formatCurrency
 #' @param method the method(s) to convert a date to string in JavaScript; see
@@ -210,6 +222,12 @@ tplSignif = function(cols, digits, interval, mark, dec.mark, ...) {
   )
 }
 
+tplExp = function(cols, digits, interval, mark, dec.mark, ...) {
+  sprintf(
+    "DTWidget.formatExp(this, row, data, %d, %d, %d, '%s', '%s');",
+    cols, digits, interval, mark, dec.mark
+  )
+}
 tplDate = function(cols, method, params, ...) {
   params = if (length(params) > 0) paste(',', toJSON(params)) else ''
   sprintf("DTWidget.formatDate(this, row, data, %d, '%s'%s);", cols, method, params)

inst/htmlwidgets/datatables.js

@@ -8,8 +8,9 @@
 var DTWidget = {};
 
 // 123456666.7890 -> 123,456,666.7890
-var markInterval = function(d, digits, interval, mark, decMark, precision) {
+var markInterval = function(d, digits, interval, mark, decMark, precision, exponential) {
   x = precision ? d.toPrecision(digits) : d.toFixed(digits);
+  if(exponential) {x = exponential ? d.toExponential(digits) : d.toFixed(digits);};
   if (!/^-?[\d.]+$/.test(x)) return x;
   var xv = x.split('.');
   if (xv.length > 2) return x;  // should have at most one decimal point
@@ -53,6 +54,13 @@ DTWidget.formatSignif = function(thiz, row, data, col, digits, interval, mark, d
     .html(markInterval(d, digits, interval, mark, decMark, true));
 };
 
+DTWidget.formatExp = function(thiz, row, data, col, digits, interval, mark, decMark) {
+  var d = parseFloat(data[col]);
+  if (isNaN(d)) return;
+  $(thiz.api().cell(row, col).node())
+    .html(markInterval(d, digits, interval, mark, decMark, false,true));
+};
+
 DTWidget.formatDate = function(thiz, row, data, col, method, params) {
   var d = data[col];
   if (d === null) return;