Fix meteorogram tick labels when they did not match the stored data

This is the proper fix for !19 (merged).

content/js/meteorogram/plot/ticks.js

@@ -42,6 +42,10 @@ function getSpeedMPH(val) {
     // convert m/s to mph
     return val * 3600 / 1608;
 }
+function getSpeedKnotsToMPH(val) {
+    // convert knots to mph
+    return val * 1.15078;
+}
 function getSpeedKTS(val) {
     //m/s to knots
     return val * 1.94384;
@@ -58,6 +62,10 @@ function getAccumMillimeter(val) {
     // convert inches to millimeters
     return val * 25.4;
 }
+function getAccumMillimeterToInches(val) {
+    // convert millimeters to inches
+    return val / 25.4;
+}
 
 
 function cardinalWDir(degrees){
@@ -83,7 +91,9 @@ var CONVERSION_FUNCTIONS = {
     getF: getF,
     getPresInHg: getPresInHg,
     getSpeedMPH: getSpeedMPH,
+    getSpeedKnotsToMPH: getSpeedKnotsToMPH,
     getAccumMillimeter: getAccumMillimeter,
+    getAccumMillimeterToInches: getAccumMillimeterToInches,
     cardinalWDir: cardinalWDir,
     getSpeedKTS:getSpeedKTS
 };
@@ -197,9 +207,26 @@ function getTickVals(min, max, bump) {
 }
 
 
+function preConvertValue(values, axis_info) {
+    /**
+     * Convert values before inserting them into the final storage array.
+     */
+    if (!('preconvert_value' in axis_info)) {
+        return;
+    }
+    var val;
+    for (var i=0; i < values.length; i++) {
+        val = CONVERSION_FUNCTIONS[axis_info.preconvert_value](values[i]);
+        val = (val.toFixed)?val.toFixed(axis_info.precision):val;
+        values[i] = val;
+    }
+}
+
+
 module.exports.getTickVals = getTickVals;
 module.exports.getProbeText = getProbeText;
 module.exports.getTickText = getTickText;
+module.exports.preConvertValue = preConvertValue;