Fixed an issue where plots for multi-key fits where not rendered corr…

…ectly

This addresses one comment in #10

example/multi_key_example.py

@@ -0,0 +1,43 @@
+"""Example script for fit with multiple keys.
+
+See also https://github.com/ckoerber/lsqfit-gui/issues/10
+"""
+import lsqfit
+import gvar as gv
+import numpy as np
+
+from lsqfitgui import run_server
+
+XX = dict(
+    d1=np.array([1, 2, 3, 4]),
+    d2=np.array([1, 2, 3, 4]),
+    d3=np.array([1, 2, 3, 4]),
+    d4=np.array([1, 2, 3, 4]),
+    d5=np.array([5, 6, 7, 8]),
+)
+
+YY = dict(
+    d1=["1.154(10)", "2.107(16)", "3.042(22)", "3.978(29)"],
+    d2=["0.692(10)", "1.196(16)", "1.657(22)", "2.189(29)"],
+    d3=["0.107(10)", "0.030(16)", "-0.027(22)", "-0.149(29)"],
+    d4=["0.002(10)", "-0.197(16)", "-0.382(22)", "-0.627(29)"],
+    d5=["1.869(10)", "2.198(16)", "2.502(22)", "2.791(29)"],
+)
+PRIOR = gv.gvar(dict(a="0(1)", s1="0(1)", s2="0(1)", s3="0(1)", s4="0(1)", s5="0(1)"))
+
+
+def fitfcn(x, p):
+    """Return linear fit function.
+
+    $$f(x; a, s_n) = a + s_n * x$$
+    """
+    return {key: p["a"] + p[f"s{key[1:]}"] * x[key] for key in x}
+
+
+def main():
+    """Run lsqfitgui server for multi-linear fit."""
+    run_server(lsqfit.nonlinear_fit(data=(XX, YY), fcn=fitfcn, prior=PRIOR))
+
+
+if __name__ == "__main__":
+    main()

lsqfitgui/plot/fit.py

@@ -56,7 +56,7 @@ def plot_fit(fit, fig: Optional[Figure] = None):
             )
             plot_band(
                 fig,
-                x_fit if isinstance(x_fit, dict) else x_fit,
+                x_fit[key] if isinstance(x_fit, dict) else x_fit,
                 y_min_fit[key],
                 y_mean_fit[key],
                 y_max_fit[key],