Plotting inequalities domain comb-style with JSXGraph

Question

I want to draw axis line with comb-styled selection of inequality domain, like in this picture:

Is it possible with JSXGraph?

Answer 1

It is not built-in to JSXGraph, yet. But this is good suggestion. Here is an implementation (to be built-in, it had to be rewritten as JSXGraph element).

const board = JXG.JSXGraph.initBoard('jxgbox', {
                            boundingbox: [-5, 5, 5, -5],
              axis: true
          });

var comb = function(board, [left, right, n, base, height]) {
    var delta,
        c = board.create('curve', [[0], [0]]);

    delta = (right - left) / n;

    c.updateDataArray = function() {
        var s;

        this.dataX = [];
        this.dataY = [];
        for (s = left; s + delta*0.5<= right; s += delta) {
            this.dataX.push(s);
            this.dataY.push(base);
            this.dataX.push(s + delta);
            this.dataY.push(base + height);
            this.dataX.push(NaN);  // Force a jump
            this.dataY.push(NaN);
        }
    };

    board.update();

    return c;  
};


var c1 = comb(board, [1, 3, 10, 0, 0.2]);
var c2 = comb(board, [-4, -1, 20, -2, 0.2]);

See it in action here: https://jsfiddle.net/vcL7aepo/217/ .