how to add a legend for multiple curves?

[timotheecour]

eg:

analog to matlab's legend:

legend('sin(x)','cos(x)')

https://www.mathworks.com/help/matlab/creating_plots/add-title-axis-labels-and-legend-to-graph.html

looked at continousLegend+friends (https://blackedder.github.io/ggplotd/ggplotd/legend.html) but couldn't find the above functionality

[BlackEdder]

Legends are inferred from the colour names, i.e.

#!/usr/bin/env dub
/+ dub.sdl:
	name "myscript"
	dependency "ggplotd" version="~>1.1.3"
+/

import std.algorithm : map;
import std.math : sin, cos;
import std.typecons : tuple;
import ggplotd.stat : statFunction; 
import ggplotd.ggplotd : GGPlotD; 
import ggplotd.geom : geomLine, geomPoint;
import ggplotd.aes : aes, merge;
import ggplotd.legend : discreteLegend;

void main() {
    auto sinF = (double x) {return sin(x);};
    auto sinAes =  statFunction(sinF, 0.0, 6.3).
        map!((a) => a.merge(aes!("colour")("sin(x)")));

    auto cosF = (double x) {return cos(x);};
    auto cosAes =  statFunction(cosF, 0.0, 6.3).
        map!((a) => a.merge(aes!("colour")("cos(x)")));
 

    auto gg = GGPlotD();
    gg = gg.put(sinAes.geomLine)
        .put(cosAes.geomLine)
        .put(discreteLegend);

    gg.save("legend.png");
}

As a side note, the API is very much inspired by ggplot2, so most things works similar to that.

[Droggelbecher]

I'm having trouble reproducing this solution.
With ggplotd-1.1.6 (via dub), this reproducibly throws an assertion error:

core.exception.AssertError@../../../.dub/packages/ggplotd-1.1.6/ggplotd/source/ggplotd/guide.d(539): Value not in storeHash
----------------
0x7ff5b023063d onAssertErrorMsg
        ???:0
0x7ff5b194b238 __lambda5
        ../../../.dub/packages/ggplotd-1.1.6/ggplotd/source/ggplotd/guide.d:539
0x7ff5b18a2a3e const std.experimental.color.rgb.RGB!("rgba", double, false, 0).RGB ggplotd.guide.GuideToColourFunction.opCall!(immutable(char)[]).opCall(const(immutable(char)[]), bool)
        ../../../.dub/packages/ggplotd-1.1.6/ggplotd/source/ggplotd/guide.d:400

[BlackEdder]

For me this is still working. Which dlang and dub versions are you using?

[Droggelbecher]

% dub --version
DUB version 1.8.0-2, built on Mar 27 2018

% gdc --version
gdc (Ubuntu 8.2.0-1ubuntu2~18.04) 8.2.0

(__VERSION__ for that one is 2068L)

Os is Ubuntu on WSL

[BlackEdder]

Sorry for the delay, but I just tested with the newest dmd: http://downloads.dlang.org/releases/2.x/2.084.0/dmd_2.084.0-0_amd64.deb
and it is working fine for me. This strongly suggest it is a gdc bug. You could try removing line 539 in guide.d, but that would probably result in further errors.

I'd suggest installing the newest dmd version from the link above.