Add minexponent axis attribute to control which powers of 10 are displayed with SI prefixes

src/components/colorbar/attributes.js

@@ -173,6 +173,7 @@ module.exports = overrideAll({
     showticksuffix: axesAttrs.showticksuffix,
     separatethousands: axesAttrs.separatethousands,
     exponentformat: axesAttrs.exponentformat,
+    minexponent: axesAttrs.minexponent,
     showexponent: axesAttrs.showexponent,
     title: {
         text: {

src/components/colorbar/draw.js

@@ -683,6 +683,7 @@ function mockColorBarAxis(gd, opts, zrange) {
         tickangle: opts.tickangle,
         tickformat: opts.tickformat,
         exponentformat: opts.exponentformat,
+        minexponent: opts.minexponent,
         separatethousands: opts.separatethousands,
         showexponent: opts.showexponent,
         showtickprefix: opts.showtickprefix,

src/plots/cartesian/axes.js

@@ -1042,7 +1042,8 @@ function autoTickRound(ax) {
 
         var maxend = Math.max(Math.abs(rng[0]), Math.abs(rng[1]));
         var rangeexp = Math.floor(Math.log(maxend) / Math.LN10 + 0.01);
-        if(Math.abs(rangeexp) > 3) {
+        var minexponent = ax.minexponent === undefined ? 3 : ax.minexponent;
+        if(Math.abs(rangeexp) > minexponent) {
             if(isSIFormat(ax.exponentformat) && !beyondSI(rangeexp)) {
                 ax._tickexponent = 3 * Math.round((rangeexp - 1) / 3);
             } else ax._tickexponent = rangeexp;
@@ -1525,6 +1526,7 @@ function numFormat(v, ax, fmtoverride, hover) {
         // make a dummy axis obj to get the auto rounding and exponent
         var ah = {
             exponentformat: exponentFormat,
+            minexponent: ax.minexponent,
             dtick: ax.showexponent === 'none' ? ax.dtick :
                 (isNumeric(v) ? Math.abs(v) || 1 : 1),
             // if not showing any exponents, don't change the exponent

src/plots/cartesian/layout_attributes.js

@@ -680,6 +680,17 @@ module.exports = {
             'If *B*, 1B.'
         ].join(' ')
     },
+    minexponent: {
+        valType: 'number',
+        dflt: 3,
+        min: 0,
+        role: 'style',
+        editType: 'ticks',
+        description: [
+            'Hide SI prefix for 10^n if |n| is below this number.',
+            'This only has an effect when `tickformat` is *SI* or *B*.'
+        ].join(' ')
+    },
     separatethousands: {
         valType: 'boolean',
         dflt: false,

src/plots/cartesian/tick_label_defaults.js

@@ -72,6 +72,7 @@ function handleOtherDefaults(containerIn, containerOut, coerce, axType, options)
             if(!tickFormat && axType !== 'date') {
                 coerce('showexponent', showAttrDflt);
                 coerce('exponentformat');
+                coerce('minexponent');
                 coerce('separatethousands');
             }
         }

src/plots/gl3d/layout/axis_attributes.js

@@ -108,6 +108,7 @@ module.exports = overrideAll({
     showticksuffix: axesAttrs.showticksuffix,
     showexponent: axesAttrs.showexponent,
     exponentformat: axesAttrs.exponentformat,
+    minexponent: axesAttrs.minexponent,
     separatethousands: axesAttrs.separatethousands,
     tickformat: axesAttrs.tickformat,
     tickformatstops: axesAttrs.tickformatstops,

src/plots/polar/layout_attributes.js

@@ -47,6 +47,7 @@ var axisTickAttrs = overrideAll({
     ticksuffix: axesAttrs.ticksuffix,
     showexponent: axesAttrs.showexponent,
     exponentformat: axesAttrs.exponentformat,
+    minexponent: axesAttrs.minexponent,
     separatethousands: axesAttrs.separatethousands,
     tickfont: axesAttrs.tickfont,
     tickangle: axesAttrs.tickangle,

src/plots/ternary/layout_attributes.js

@@ -40,6 +40,7 @@ var ternaryAxesAttrs = {
     ticksuffix: axesAttrs.ticksuffix,
     showexponent: axesAttrs.showexponent,
     exponentformat: axesAttrs.exponentformat,
+    minexponent: axesAttrs.minexponent,
     separatethousands: axesAttrs.separatethousands,
     tickfont: axesAttrs.tickfont,
     tickangle: axesAttrs.tickangle,

src/traces/carpet/axis_attributes.js

@@ -284,6 +284,16 @@ module.exports = {
             'If *B*, 1B.'
         ].join(' ')
     },
+    minexponent: {
+        valType: 'number',
+        dflt: 3,
+        min: 0,
+        role: 'style',
+        editType: 'calc',
+        description: [
+            'Hide SI prefix for 10^n if |n| is below this number'
+        ].join(' ')
+    },
     separatethousands: {
         valType: 'boolean',
         dflt: false,

src/traces/carpet/axis_defaults.js

@@ -78,6 +78,7 @@ module.exports = function handleAxisDefaults(containerIn, containerOut, options)
     coerce('separatethousands');
     coerce('tickformat');
     coerce('exponentformat');
+    coerce('minexponent');
     coerce('showexponent');
     coerce('categoryorder');
 
@@ -186,6 +187,7 @@ module.exports = function handleAxisDefaults(containerIn, containerOut, options)
         delete containerOut.tickangle;
         delete containerOut.showexponent;
         delete containerOut.exponentformat;
+        delete containerOut.minexponent;
         delete containerOut.tickformat;
         delete containerOut.showticksuffix;
         delete containerOut.showtickprefix;

src/traces/indicator/attributes.js

@@ -355,6 +355,7 @@ module.exports = {
             showticksuffix: axesAttrs.showticksuffix,
             separatethousands: axesAttrs.separatethousands,
             exponentformat: axesAttrs.exponentformat,
+            minexponent: axesAttrs.minexponent,
             showexponent: axesAttrs.showexponent,
             editType: 'plot'
         }, 'plot'),

test/jasmine/tests/axes_test.js

@@ -2851,6 +2851,58 @@ describe('Test axes', function() {
             ]);
         });
 
+        it('Does not use SI prefixes for 10^n with |n| < minexponent', function() {
+            var textOut = mockCalc({
+                type: 'log',
+                tickmode: 'linear',
+                exponentformat: 'SI',
+                minexponent: 5,
+                showexponent: 'all',
+                tick0: 0,
+                dtick: 1,
+                range: [-18.5, 18.5]
+            });
+
+            expect(textOut).toEqual([
+                '10<sup>\u221218</sup>',
+                '10<sup>\u221217</sup>',
+                '10<sup>\u221216</sup>',
+                '1f', '10f', '100f', '1p', '10p', '100p', '1n', '10n', '100n',
+                '1μ', '0.00001', '0.0001', '0.001', '0.01', '0.1', '1', '10', '100',
+                '1000', '10,000', '100,000', '1M', '10M', '100M', '1G', '10G', '100G',
+                '1T', '10T', '100T',
+                '10<sup>15</sup>',
+                '10<sup>16</sup>',
+                '10<sup>17</sup>',
+                '10<sup>18</sup>'
+            ]);
+
+            textOut = mockCalc({
+                type: 'log',
+                tickmode: 'linear',
+                exponentformat: 'SI',
+                minexponent: 0,
+                showexponent: 'all',
+                tick0: 0,
+                dtick: 1,
+                range: [-18.5, 18.5]
+            });
+
+            expect(textOut).toEqual([
+                '10<sup>\u221218</sup>',
+                '10<sup>\u221217</sup>',
+                '10<sup>\u221216</sup>',
+                '1f', '10f', '100f', '1p', '10p', '100p', '1n', '10n', '100n',
+                '1μ', '10μ', '100μ', '1m', '10m', '100m', '1', '10', '100',
+                '1k', '10k', '100k', '1M', '10M', '100M', '1G', '10G', '100G',
+                '1T', '10T', '100T',
+                '10<sup>15</sup>',
+                '10<sup>16</sup>',
+                '10<sup>17</sup>',
+                '10<sup>18</sup>'
+            ]);
+        });
+
         it('supports e/E format on log axes', function() {
             ['e', 'E'].forEach(function(e) {
                 var textOut = mockCalc({