From 69866135a8f0955196a26162afa4c90b9a5232e4 Mon Sep 17 00:00:00 2001
From: Aaron LI <aaronly.me@outlook.com>
Date: Wed, 4 May 2016 21:02:53 +0800
Subject: info.py: new; handy functions to get information from INFO.json

---
 info.py | 67 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 67 insertions(+)
 create mode 100644 info.py

diff --git a/info.py b/info.py
new file mode 100644
index 0000000..14d5fd1
--- /dev/null
+++ b/info.py
@@ -0,0 +1,67 @@
+#
+# Aaron LI
+# Created: 2016-05-04
+# Updated: 2016-05-04
+#
+
+"""
+module to process the INFO.json file, contains some handy functions
+to extract the needed information.
+"""
+
+import json
+
+
+def load_info(info):
+    """
+    Load data from the INFO.json if necessary.
+    """
+    if isinstance(info, str):
+        json_str = open(info).read().rstrip().rstrip(",")
+        return json.loads(json_str)
+    else:
+        # assuming that the provided `info` is already a Python dictionary
+        return info
+
+
+def get_r500(info):
+    """
+    Get the R500 value (in unit pixel and kpc), as well as its errors.
+
+    Arguments:
+      * info: filename of the INFO.json, or the info dictionary
+
+    Return:
+      a dictionary contains the necessary results
+    """
+    info = load_info(info)
+
+    if "IN_SAMPLE" in info.keys():
+        # ZZH's INFO
+        r500_kpc = float(info["R500"])
+        r500EL_kpc = float(info["R500_err_lower"])
+        r500EU_kpc = float(info["R500_err_upper"])
+    else:
+        # LWT's INFO
+        r500_kpc = float(info["R500 (kpc)"])
+        r500EL_kpc = float(info["R500_err_lower (1sigma)"])
+        r500EU_kpc = float(info["R500_err_upper (1sigma)"])
+
+    # Convert kpc to Chandra ACIS pixel
+    rmax_sbp_pix = float(info["Rmax_SBP (pixel)"])
+    rmax_sbp_kpc = float(info["Rmax_SBP (kpc)"])
+    kpc_per_pix = rmax_sbp_kpc / rmax_sbp_pix
+    r500_pix = r500_kpc / kpc_per_pix
+    r500EL_pix = r500EL_kpc / kpc_per_pix
+    r500EU_pix = r500EU_kpc / kpc_per_pix
+
+    results = {
+            "r500_kpc":    r500_kpc,
+            "r500EL_kpc":  r500EL_kpc,
+            "r500EU_kpc":  r500EU_kpc,
+            "r500_pix":    r500_pix,
+            "r500EL_pix":  r500EL_pix,
+            "r500EU_pix":  r500EU_pix,
+            "kpc_per_pix": kpc_per_pix,
+    }
+    return results
-- 
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