plot_sayma_data: Add option to skip data plotting

plot_sayma_data.py

@@ -31,6 +31,9 @@ def main():
     parser.add_argument("--log",
         help="path of the log file where the measurement record will be appended",
         type=str)
+    parser.add_argument("--noplot",
+        help="do not show data plot, which is blocking until the GUI is closed",
+        action="store_true")
     args = parser.parse_args()
 
     # Must only compare 2 data
@@ -77,6 +80,7 @@ def main():
     # Print the phase difference
     print(angle)
 
+    if not args.noplot:
         # Normalize y1 and y2 for plotting
         y1 /= abs(y1).max()
         y2 /= abs(y2).max()