! Example of heatmap with black/white numeric labels.
! Author: Francois Tonneau

size 22 14

set font ss hei 0.3

include palettes.gle

! Draw the frame around the map via a graph block.

amove 3 2
begin graph
    size 14 10
    fullsize
    xaxis min 0 max 12 ftick 0.5 dticks 1
    yaxis min 0 max 12 ftick 0.5 dticks 1
    xtitle Year adist 0.9
    ytitle Month adist 1.2
    side off
    ticks off
    xlabels off
    x2labels off
    ylabels off
    y2labels off
	labels hei 0.4
    data "heatmap.dat"
    xnames 1949 1950 1951 1952 1953 1954 1955 1956 1957 1958 1959 1960
    ynames Dec Nov Oct Sep Aug Jul Jun May Apr Mar Feb Jan
end graph

! Draw the map.

low = 100
high = 630

dx = xg(2) - xg(1)
dy = yg(2) - yg(1)

sub adjusted z
    return (z - low) / (high - low)
end sub

for col = 1 to ndatasets()
    n = ndata(d[col])
    for row = 1 to n
        z = datayvalue(d[col], row)
        amove xg(col - 1) yg(n - row)
        set color white lwidth 0.01
        box dx dy just bl fill magma(adjusted(z))
        rmove 0.33 0.32
        set color magma_text(adjusted(z))
        write z
    next row
next col

! Add a custom color ramp on the right.

low = 70        ! => stretch the ramp down for prettier looks
high = 630
dy = 0.015

amove 19 2.8
for z = low to high
    set color magma(adjusted(z)) lwidth 0
    box 0.8 dy just bl fill magma(adjusted(z))
    rmove 0 dy
next z
set color gray50 lwidth 0.03 just lc

amove 20 2.8+(30*dy)
for tick = 100 to 600 step 100
    write tick
    rmove 0 1.5
next tick