RankSum params

Hi,

Why MQRankSum ReadPosRankSum is calculated for some variants but not all ? Below are 2 variants from same file.

X 33032663 . A T 19668.77 PASS AC=2;AF=1.00;AN=2;DP=450;ExcessHet=3.0103;FS=0.000;MLEAC=2;MLEAF=1.00;MQ=69.29;QD=31.36;SOR=0.744 GT:AD:DP:GQ:PL 1/1:0,443:443:99:19697,1375,0
X 33032763 . A T 3446.77 PASS AC=1;AF=0.500;AN=2;BaseQRankSum=-8.904;ClippingRankSum=-0.924;DP=281;ExcessHet=3.0103;FS=5.348;MLEAC=1;MLEAF=0.500;MQ=69.65;MQRankSum=0.060;QD=12.40;ReadPosRankSum=-0.989;SOR=1.068 GT:AD:DP:GQ:PL 0/1:141,137:278:99:3475,0,3781

Swati