Polar plot with 0° at the nadir?

Specific Domains Visualization
4

Yeah, doesn’t seem GR supports this.
But this can be forced by digging into Plots.jl.

Try the following code:

Big function here... 
import Plots: gr_polaraxes

function gr_polaraxes(rmin::Real, rmax::Real, sp::Plots.Subplot)
    GR.savestate()
    xaxis = sp[:xaxis]
    yaxis = sp[:yaxis]

    orig_α = 0:45:315
    a = orig_α .+ 90
    sinf = sind.(a)
    cosf = cosd.(a)
    α = collect(circshift(orig_α, 2))
    rtick_values, rtick_labels = Plots.get_ticks(sp, yaxis, update = false)

    # draw angular grid                                                                                                                                               
    if xaxis[:grid]
        Plots.gr_set_line(
            xaxis[:gridlinewidth],
            xaxis[:gridstyle],
            xaxis[:foreground_color_grid],
            sp,
        )
        Plots.gr_set_transparency(xaxis[:foreground_color_grid], xaxis[:gridalpha])
        for i in eachindex(α)
            GR.polyline([sinf[i], 0], [cosf[i], 0])
        end
    end

    # draw radial grid                                                                                                                                                
    if yaxis[:grid]
        Plots.gr_set_line(
            yaxis[:gridlinewidth],
            yaxis[:gridstyle],
            yaxis[:foreground_color_grid],
            sp,
        )
        Plots.gr_set_transparency(yaxis[:foreground_color_grid], yaxis[:gridalpha])
        for i in eachindex(rtick_values)
            r = (rtick_values[i] - rmin) / (rmax - rmin)
            if r <= 1.0 && r >= 0.0
                GR.drawarc(-r, r, -r, r, 0, 359)
            end
        end
        GR.drawarc(-1, 1, -1, 1, 0, 359)
    end

    # prepare to draw ticks                                                                                                                                           
    Plots.gr_set_transparency(1)
    GR.setlinecolorind(90)
    GR.settextalign(GR.TEXT_HALIGN_CENTER, GR.TEXT_VALIGN_HALF)

    # draw angular ticks                                                                                                                                              
    if xaxis[:showaxis]
        GR.drawarc(-1, 1, -1, 1, 0, 359)
        for i in eachindex(α)
            x, y = GR.wctondc(1.1 * sinf[i], 1.1 * cosf[i])
            GR.textext(x, y, string((360 - α[i]) % 360, "^o"))
        end
    end

    # draw radial ticks                                                                                                                                               
    if yaxis[:showaxis]
        for i in eachindex(rtick_values)
            r = (rtick_values[i] - rmin) / (rmax - rmin)
            if r <= 1.0 && r >= 0.0
                x, y = GR.wctondc(0.05, r)
                Plots.gr_text(x, y, Plots._cycle(rtick_labels, i))
            end
        end
    end
    GR.restorestate()
end

This did it on my machine:

julia> plot(r, 0, 2π, proj=:polar, lims=(0,1.5));

gives:

polarplot
polarplot1079×778 64.3 KB

Note, the series didn’t really change, only the axis labels, so it might be easiest to transform the data series to fit the new labels (or dig more into the code).

Plots.jl did not intend for this feature to exist… yet.

The changed bit is the:

orig_α = 0:45:315
a = orig_α .+ 90

α = collect(circshift(orig_α, 2))

at the beginning.