function highlightBrushPoints(data) {
        if (data.date.getTime() >= brush.extent()[0].getTime() && data.date.getTime() <= brush.extent()[1].getTime()) {
            return 1
        } else {
            return 0.2
        }
    }
// get the desired opacity for context chart based on the brush extent
get the desired opacity for context chart based on the brush extent
get the desired opacity for context chart based on the brush extent
function highlightBrushPoints(data) {
        if (data.date.getTime() >= brush.extent()[0].getTime() && data.date.getTime() <= brush.extent()[1].getTime()) {
            return 1
        } else {
            return 0.2
        }
    }
function highlightBrushPoints ( data ) { if ( data . date . getTime ( ) >= brush . extent ( ) [ 0 ] . getTime ( ) && data . date . getTime ( ) <= brush . extent ( ) [ 1 ] . getTime ( ) ) { return 1 } else { return 0.2 } }
get the desired opacity for context chart based on the brush extent
get the desired opacity for context chart based on the brush extent