Add "SI extended" formatting rule for the tick exponents

src/plots/cartesian/axes.js

@@ -1558,7 +1558,8 @@ function autoTickRound(ax) {
         var rangeexp = Math.floor(Math.log(maxend) / Math.LN10 + 0.01);
         var minexponent = ax.minexponent === undefined ? 3 : ax.minexponent;
         if(Math.abs(rangeexp) > minexponent) {
-            if(isSIFormat(ax.exponentformat) && !beyondSI(rangeexp)) {
+            if((isSIFormat(ax.exponentformat) && ax.exponentformat !== 'SI extended' && !beyondSI(rangeexp)) || 
+            (isSIFormat(ax.exponentformat) && ax.exponentformat === 'SI extended' && !beyondSIExtended(rangeexp))) {
                 ax._tickexponent = 3 * Math.round((rangeexp - 1) / 3);
             } else ax._tickexponent = rangeexp;
         }
@@ -1904,7 +1905,8 @@ function formatLog(ax, out, hover, extraPrecision, hideexp) {
         var p = Math.round(x);
         var absP = Math.abs(p);
         var exponentFormat = ax.exponentformat;
-        if(exponentFormat === 'power' || (isSIFormat(exponentFormat) && beyondSI(p))) {
+        if(exponentFormat === 'power' || (isSIFormat(exponentFormat) && exponentFormat !== 'SI extended' && beyondSI(p)) ||
+        (isSIFormat(exponentFormat) && exponentFormat === 'SI extended' && beyondSIExtended(p))) {
             if(p === 0) out.text = 1;
             else if(p === 1) out.text = '10';
             else out.text = '10<sup>' + (p > 1 ? '' : MINUS_SIGN) + absP + '</sup>';
@@ -2049,8 +2051,11 @@ function num2frac(num) {
 // also automatically switch to sci. notation
 var SIPREFIXES = ['f', 'p', 'n', 'μ', 'm', '', 'k', 'M', 'G', 'T'];
 
+// extending SI prefixes
+var SIPREFIXES_EXTENDED = ['q', 'r', 'y', 'z', 'a', 'f', 'p', 'n', 'μ', 'm', '', 'k', 'M', 'G', 'T', 'P', 'E', 'Z', 'Y', 'R', 'Q'];
+
 function isSIFormat(exponentFormat) {
-    return exponentFormat === 'SI' || exponentFormat === 'B';
+    return exponentFormat === 'SI' || exponentFormat === 'SI extended' || exponentFormat === 'B';
 }
 
 // are we beyond the range of common SI prefixes?
@@ -2064,6 +2069,10 @@ function beyondSI(exponent) {
     return exponent > 14 || exponent < -15;
 }
 
+function beyondSIExtended(exponent) {
+    return exponent > 32 || exponent < -30;
+}
+
 function numFormat(v, ax, fmtoverride, hover) {
     var isNeg = v < 0;
     // max number of digits past decimal point to show
@@ -2139,7 +2148,8 @@ function numFormat(v, ax, fmtoverride, hover) {
 
     // add exponent
     if(exponent && exponentFormat !== 'hide') {
-        if(isSIFormat(exponentFormat) && beyondSI(exponent)) exponentFormat = 'power';
+        if((isSIFormat(exponentFormat) && exponentFormat !== 'SI extended' && beyondSI(exponent)) ||
+        (isSIFormat(exponentFormat) && exponentFormat === 'SI extended' && beyondSIExtended(exponent))) exponentFormat = 'power';
 
         var signedExponent;
         if(exponent < 0) signedExponent = MINUS_SIGN + -exponent;
@@ -2153,7 +2163,11 @@ function numFormat(v, ax, fmtoverride, hover) {
         } else if(exponentFormat === 'B' && exponent === 9) {
             v += 'B';
         } else if(isSIFormat(exponentFormat)) {
-            v += SIPREFIXES[exponent / 3 + 5];
+            if(exponentFormat !== 'SI extended') {
+                v += SIPREFIXES[exponent / 3 + 5];
+            } else if(exponentFormat === 'SI extended') {
+                v += SIPREFIXES_EXTENDED[exponent / 3 + 10];
+            }
         }
     }
 

src/plots/cartesian/layout_attributes.js

@@ -897,7 +897,7 @@ module.exports = {
     },
     exponentformat: {
         valType: 'enumerated',
-        values: ['none', 'e', 'E', 'power', 'SI', 'B'],
+        values: ['none', 'e', 'E', 'power', 'SI', 'B', 'SI extended'],
         dflt: 'B',
         editType: 'ticks',
         description: [
@@ -908,7 +908,12 @@ module.exports = {
             'If *E*, 1E+9.',
             'If *power*, 1x10^9 (with 9 in a super script).',
             'If *SI*, 1G.',
-            'If *B*, 1B.'
+            'If *B*, 1B.',
+
+            '*SI* uses prefixes from "femto" f (10^-15) to "tera" T (10^12).',
+            '*SI extended* covers instead the full SI range from "quecto" q (10^-30) to "quetta" Q (10^30).',
+            'If *SI* or *SI extended* is used and the exponent is beyond the above ranges, the formatting rule',
+            'will automatically be switched to the power notation.'
         ].join(' ')
     },
     minexponent: {

src/traces/carpet/axis_attributes.js

@@ -234,7 +234,7 @@ module.exports = {
     },
     exponentformat: {
         valType: 'enumerated',
-        values: ['none', 'e', 'E', 'power', 'SI', 'B'],
+        values: ['none', 'e', 'E', 'power', 'SI', 'B', 'SI extended'],
         dflt: 'B',
         editType: 'calc',
         description: [

test/image/mocks/20.json

@@ -8,7 +8,7 @@
   },
   {
    "x": [2, 3, 4],
-   "y": [40, 50, 60],
+   "y": [4000000000000, 5000000000000, 6000000000000],
    "name": "yaxis2 data",
    "yaxis": "y2",
    "type": "scatter"
@@ -36,7 +36,7 @@
   },
   {
    "x": [6, 7, 8],
-   "y": [4000000, 5000000, 6000000],
+   "y": [400000000000000000000000000000000, 500000000000000000000000000000000, 600000000000000000000000000000000],
    "name": "yaxis6 data",
    "yaxis": "y6",
    "type": "scatter"
@@ -111,6 +111,7 @@
    "tickfont": {
     "color": "#ff7f0e"
    },
+   "exponentformat": "SI",
    "linecolor": "rgba(255,127,14,0.4)",
    "linewidth": 6,
    "anchor": "free",
@@ -189,7 +190,7 @@
    "tickfont": {
     "color": "#8c564b"
    },
-   "exponentformat": "SI",
+   "exponentformat": "SI extended",
    "linecolor": "rgba(140,86,75,0.5)",
    "anchor": "free",
    "side": "right",