D3 mercator function NaN

Question

I'm not too familiar with the D3 mercator projection function, and I'm getting some unexpected results. I'd like to project the following latitude and longitude (somewhere in Mexico):

var geo = [19, -99]

I define my mercator projection using d3

var projection = d3.geo.mercator();
projection(geo)
> [529.7418836818384, NaN]

which is a point obviously not on a map. What exactly am I doing wrong? Thanks!

Answer 1

Javascript has it's lat and long round the opposite way to the rest of the world, so what you've given D3 is a longditue of 19 and a latitude of -99. Obviously there is no latitude of -99 hence the NaN. Now if you just reverse your geo variable to

var geo = [-99, 19]

all should be good.