Need to make custom reducer to deduct two values - dc.js

Question

"Date(UTC)","Market","Type","Price","Amount","Total","Fee","Fee Coin"
12:18:07","ETCBTC","BUY","0.002064","1.05","0.00216720","0.00105","ETC"
"2018-05-26 06:01:12","ETCBTC","SELL","0.00207","5.86","0.01213020","0.00001213","BTC"
"2018-05-25 22:47:14","ETCBTC","BUY","0.002","1.32","0.00264000","0.00132","ETC"
This is part of my dataset. The problem is that in my data set "Total" that I need to use is just numbers - to make them work I have to connect them with "Type" (BUY/SELL).
BUY should work like "-" and SELL like "+"; the difference between them is that what I need to display.
I am just learning. So I didn't try a lot.
function show_profit(ndx) {
var typeDim = ndx.dimension(dc.pluck("Type"));
var profit = typeDim.group().reduce(
function (p, v) {
p.count++;
p.total += v.Total;
return p;
},
function (p, v) {
p.count--;
p.total -= v.Total;
return p;
},
function () {
return { count:0, total: 0};
}
);
dc.barChart("#profit")
.width(500)
.height(300)
.dimension(typeDim)
.group(profit)
.valueAccessor(function (d) {
if (d.value.count == 0) {
return 0;
} else {
return d.value.total;
}
})
.transitionDuration(500)
.x(d3.scale.ordinal())
.xUnits(dc.units.ordinal)
.elasticY(true)
.xAxisLabel("Type")
.yAxisLabel("Amount")
.yAxis().ticks(20);
}
I just made graph with volume per BUY and SELL.
My target is to find the difference between BUY and SELL and display it in a line graph.

Answer 1

I'm not sure if I understand your question completely, but if you simply want to apply SELL as positive and BUY as negative, you should be able to multiply the values by 1 or -1 in your reduction functions:
function mult(type) {
switch(type) {
case 'SELL': return 1;
case 'BUY': return -1;
default: throw new Error('unknown Type ' + type);
}
var profit = typeDim.group().reduce(
function (p, v) {
p.count++;
p.total += mult(v.Type) * v.Total;
return p;
},
function (p, v) {
p.count--;
p.total -= mult(v.Type) * v.Total;
return p;
},
function () {
return { count:0, total: 0};
}
);