Expression
Simple Expression Example
This function is only available for Layers that has the ‘source’ as ‘calculated’.
The ‘expression()’ function is executed for every pixel in the map. In this function, you can filter, combine or handle the map information however you would like. It uses JavaScript syntax and has access to all of its functionalities.
Besides that, the function receives two parameters: ‘layerVals’ and ‘inputs’.
layerVals: Is an array of values of the actual pixels being processed. The values are in the same order as they were defined in the ‘name’ property. For example, if the name property is: “name: ‘CSR:geologia,CSR:solos’”, the ‘layerVals[0]’ has the value of the ‘CSR:geologia’ map and the ‘layerVals[1]’ has the value of the ‘CSR:solos’ map.
inputs: Is an array of values of the tools defined in the ‘descriptionHtml’. Likewise the ‘layerVals’, the ‘inputs’ values are in the same order as the tools were declared at the ‘descriptionHtml’. For example, if the descriptionHtml has 2 Textfield. the ‘inputs[0]’ will be the value of the first input and the ‘inputs[1]’ is the value of the second.
[
{
title: 'Example of expression function',
color: '#FFA500',
elements: [
{
title: 'This Layer is the result of the calculation of two maps',
name: 'CSR:geologia,CSR:altimetria',
source: 'calculate',
legendTitle: 'All geologys above 800m',
visibility: true,
expression: function(layerVals, inputs) {
let geologyValue = layerVals[0];
let altitudeValue = layerVals[1];
// Hide all values lower than 800
if (altitudeValue < 800) {
return undefined;
}
return geologyValue;
},
},
],
},
]
