feat: working on residual plots

src/plotting-recipes.jl

@@ -127,7 +127,13 @@ end
 # residual plots
 # note: multiple datasets require repeated calls to this function (write a wrapper later)
 @userplot ResidualPlot
-@recipe function _plotting_fun(r::ResidualPlot)
+@recipe function _plotting_fun(
+    r::ResidualPlot,
+    datacolor = :auto,
+    modelcolor = :auto,
+    residualcolor = :auto,
+    label = :auto,
+)
     # check that the function has been passed one dataset and one fit result
     if length(r.args) != 2 ||
        !(typeof(r.args[1]) <: AbstractDataset) ||
@@ -146,9 +152,90 @@ end
     result = r.args[2] isa FittingResult ? r.args[2][1] : r.args[2]
     y = invoke_result(result, result.u)
 
-    y_residual = @. y - result.objective
+    # residual is the difference between the model and the data in units of "sigma" so the error bars have size 1
+    # this assumes we have statistics such that sigma = sqrt(variance) - should probably make this more statistically neutral
+    y_residual = @. (result.objective - y) / sqrt(result.variance)
+    # is this the best way to ensure y_residual_error has the same type as y_residual, or should it just be fixe at Float64?
+    y_residual_error = ones(eltype(y_residual), length(y_residual))
 
-    ylabel --> "Residual [data - model]"
-    xlabel --> "Energy (keV)"
     minorgrid --> true
+
+    if (label == :auto)
+        label = make_label(data)
+    end
+
+    # layout --> @layout [grid(2, 1, heights=[0.7 ,0.3]), margin=0mm]
+    layout --> @layout [
+        top{0.75h}
+        bottom{0.25h}
+    ]
+    bottom_margins --> (-5, :mm)
+
+    # logarithmic x-axis (might want to let this be an option)
+    xscale --> :log10
+    filtered_array = filter(x -> x != 0, result.objective)
+    min_non_zero_value = 0.8 * minimum(filtered_array)
+    max_non_zero_value = 1.2 * maximum(filtered_array)
+
+    # plot the data
+    @series begin
+        subplot --> 1
+        yscale --> :log10
+        yrange --> [min_non_zero_value, max_non_zero_value]
+        markerstrokecolor --> datacolor
+        label --> label
+        seriestype --> :scatter
+        markershape --> :none
+        markersize --> 0.5
+        yerror --> sqrt.(result.variance)
+        xerror --> bin_widths(data) ./ 2
+        x, result.objective
+    end
+
+    # plot the model - need to fix this
+    @series begin
+        subplot --> 1
+        yscale --> :log10
+        yrange --> [min_non_zero_value, max_non_zero_value]
+        xticks --> nothing
+        ylabel --> "Flux (units)"
+        markerstrokecolor --> modelcolor
+        label --> label
+        seriestype --> :scatter
+        markershape --> :none
+        markersize --> 0.5
+        xerror --> bin_widths(data) ./ 2
+        x, y
+    end
+
+    # plot the residuals
+    @series begin
+        subplot --> 2
+        yscale --> :identity
+        xticks --> true
+        xlabel --> "Energy (keV)"
+        ylabel --> "Data - model"
+        markerstrokecolor --> residualcolor
+        label --> :none
+        seriestype --> :scatter
+        markershape --> :none
+        markersize --> 0.5
+        yerror --> y_residual_error
+        xerror --> bin_widths(data) ./ 2
+        x, y_residual
+    end
+
+    # zero line
+    @series begin
+        subplot --> 2
+        yscale --> :identity
+        xticks --> true
+        xlabel --> "Energy (keV)"
+        ylabel --> "Data - model"
+        linestyle --> :dash
+        seriestype --> :hline
+        label --> false
+        # not currently specifying a colour
+        [0.0]
+    end
 end