From aca7d56f0767d1d5f87629551349cfb704fe3912 Mon Sep 17 00:00:00 2001
From: Atharva Arya <aryaa_1@rknec.edu>
Date: Thu, 29 Jul 2021 19:06:23 +0530
Subject: [PATCH] Observed Spectrum option for the matplotlib plot

---
 tardis/visualization/tools/sdec_plot.py | 30 +++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/tardis/visualization/tools/sdec_plot.py b/tardis/visualization/tools/sdec_plot.py
index 6c9d1dc5868..d14b3bb71a8 100644
--- a/tardis/visualization/tools/sdec_plot.py
+++ b/tardis/visualization/tools/sdec_plot.py
@@ -1082,6 +1082,7 @@ def generate_plot_mpl(
         packets_mode="virtual",
         packet_wvl_range=None,
         distance=None,
+        observed_spectrum=None,
         show_modeled_spectrum=True,
         ax=None,
         figsize=(12, 7),
@@ -1105,6 +1106,8 @@ def generate_plot_mpl(
         distance : astropy.Quantity or None, optional
             Distance used to calculate flux instead of luminosity in the plot.
             It should have a length unit like m, Mpc, etc. Default value is None
+        observed_spectrum : tuple or list of two astropy quantities, optional
+            Option to plot the observed spectrum.
         show_modeled_spectrum : bool, optional
             Whether to show modeled spectrum in SDEC Plot. Default value is
             True
@@ -1178,6 +1181,33 @@ def generate_plot_mpl(
                 linewidth=1,
             )
 
+        # Plot observed spectrum
+        if observed_spectrum:
+            observed_spectrum_wavelength = None
+            observed_spectrum_luminosity = None
+
+            if (
+                type(observed_spectrum[0]) is u.quantity.Quantity
+                and type(observed_spectrum[1]) is u.quantity.Quantity
+            ):
+                # If the observed spectrum is a list of quantities, then convert to wavelength and luminosity units
+                observed_spectrum_wavelength = observed_spectrum[0].to(u.AA)
+                observed_spectrum_luminosity = observed_spectrum[1].to(
+                    u.erg / (u.s)
+                )
+
+            else:
+                raise ValueError(
+                    "Both wavelength and luminosity should be astropy quantities."
+                )
+            self.ax.plot(
+                observed_spectrum_wavelength,
+                observed_spectrum_luminosity,
+                linestyle="--",
+                label="Observed Spectrum",
+                linewidth=1,
+            )
+
         # Plot photosphere
         self.ax.plot(
             self.plot_wavelength,