seqtk fqchk: fix division by zero error (#51)

* Ensure that seqtk_fqchk_data_by_position files are created

* Handle division by zero

Author: dfornika

bin/summarize_seqtk_fqchk.py

@@ -37,13 +37,21 @@ def main(args):
 
     total_bases = sum([x['num_bases'] for x in seqtk_fqchk_output])
 
-    overall_percent_gc = sum([x['percent_gc'] * x['num_bases'] for x in seqtk_fqchk_output]) / total_bases
+    percent_above_header = 'percent_bases_above_q' + str(quality_threshold)
 
-    overall_average_q = sum([x['average_q'] * x['num_bases'] for x in seqtk_fqchk_output]) / total_bases
+    if total_bases > 0:
+        overall_percent_gc = sum([x['percent_gc'] * x['num_bases'] for x in seqtk_fqchk_output]) / total_bases
 
-    percent_above_header = 'percent_bases_above_q' + str(quality_threshold)
+        overall_average_q = sum([x['average_q'] * x['num_bases'] for x in seqtk_fqchk_output]) / total_bases
+
+        overall_percent_above_threshold = sum([x[percent_above_header] * x['num_bases'] for x in seqtk_fqchk_output]) / total_bases
+    else:
+        overall_percent_gc = 0.0
+
+        overall_average_q = 0.0
+
+        overall_percent_above_threshold = 0.0
 
-    overall_percent_above_threshold = sum([x[percent_above_header] * x['num_bases'] for x in seqtk_fqchk_output]) / total_bases
 
     print(','.join([
         'sample_id',