Fix histogram deformations

app/api/formulas.py

@@ -58,11 +58,13 @@ algos = {
     },
     'LAI': {
         'expr': '3.618 * (2.5 * (N - R) / (N + 6*R - 7.5*B + 1)) * 0.118',
-        'help': 'Leaf Area Index estimates foliage areas and predicts crop yields.'
+        'help': 'Leaf Area Index estimates foliage areas and predicts crop yields.',
+        'range': (-1, 1)
     },
     'EVI': {
         'expr': '2.5 * (N - R) / (N + 6*R - 7.5*B + 1)',
-        'help': 'Enhanced Vegetation Index is useful in areas where NDVI might saturate, by using blue wavelengths to correct soil signals.'
+        'help': 'Enhanced Vegetation Index is useful in areas where NDVI might saturate, by using blue wavelengths to correct soil signals.',
+        'range': (-1, 1)
     },
 
     # more?

app/static/app/js/components/Histogram.jsx

@@ -115,6 +115,11 @@ export default class Histogram extends React.Component {
             return [band.histogram[1][i], e];
         });
 
+        // Make sure histogram starts and ends at 0
+        // to prevent oblique looking charts
+        data.unshift([data[0][0], 0]);
+        data.push([data[data.length - 1][0], 0]);
+
         // Plot the area
         svg.append('g')
            .append("path")