F1 From Counts

Grid B Precision and Recall

Read precision and recall side labels for grid B.

highlighted = computed this step

Grid B precision

Grid B precision is TP over TP plus FP: 1 over 1, which is 1.

precisionB=11=1\text{precision}_B={1\over1}=1
F1 Score ExactlyExact F1 fractions from two confusion grids.two confusion grids with exact F1 fractionsgrid Agrid A confusion gridactualpred Ppred NPTP=2FN=1NFP=1TN=1precision and recall side labelsratefractionprecision TP/(TP+FP)2/3 = 2/3recall TP/(TP+FN)2/3 = 2/3F1 denominator blocks2TP=4FP=1FN=12TP+FP+FN=6F1=4/6 = 2/3grid Bgrid B confusion gridactualpred Ppred NPTP=1FN=2NFP=0TN=2precision and recall side labelsratefractionprecision TP/(TP+FP)1/1 = 1recall TP/(TP+FN)1/3 = 1/3F1 denominator blocks2TP=2FP=0FN=22TP+FP+FN=4F1=2/4 = 1/2F1 is computed from displayed counts; denominator is 2TP plus FP plus FNdoes not claim: NOT best metric; NOT future performanceNOT accuracy; NOT calibration; NOT fairness; NOT safetyNOT generalization; NOT probability truth

Grid B recall

Grid B recall is TP over TP plus FN: 1 over 3.

recallB=13\text{recall}_B={1\over3}
F1 Score ExactlyExact F1 fractions from two confusion grids.two confusion grids with exact F1 fractionsgrid Agrid A confusion gridactualpred Ppred NPTP=2FN=1NFP=1TN=1precision and recall side labelsratefractionprecision TP/(TP+FP)2/3 = 2/3recall TP/(TP+FN)2/3 = 2/3F1 denominator blocks2TP=4FP=1FN=12TP+FP+FN=6F1=4/6 = 2/3grid Bgrid B confusion gridactualpred Ppred NPTP=1FN=2NFP=0TN=2precision and recall side labelsratefractionprecision TP/(TP+FP)1/1 = 1recall TP/(TP+FN)1/3 = 1/3F1 denominator blocks2TP=2FP=0FN=22TP+FP+FN=4F1=2/4 = 1/2F1 is computed from displayed counts; denominator is 2TP plus FP plus FNdoes not claim: NOT best metric; NOT future performanceNOT accuracy; NOT calibration; NOT fairness; NOT safetyNOT generalization; NOT probability truth

The side labels are different

For grid B, precision and recall are not the same fraction.

different denominators; different side labels\text{different denominators; different side labels}
F1 Score ExactlyExact F1 fractions from two confusion grids.two confusion grids with exact F1 fractionsgrid Agrid A confusion gridactualpred Ppred NPTP=2FN=1NFP=1TN=1precision and recall side labelsratefractionprecision TP/(TP+FP)2/3 = 2/3recall TP/(TP+FN)2/3 = 2/3F1 denominator blocks2TP=4FP=1FN=12TP+FP+FN=6F1=4/6 = 2/3grid Bgrid B confusion gridactualpred Ppred NPTP=1FN=2NFP=0TN=2precision and recall side labelsratefractionprecision TP/(TP+FP)1/1 = 1recall TP/(TP+FN)1/3 = 1/3F1 denominator blocks2TP=2FP=0FN=22TP+FP+FN=4F1=2/4 = 1/2F1 is computed from displayed counts; denominator is 2TP plus FP plus FNdoes not claim: NOT best metric; NOT future performanceNOT accuracy; NOT calibration; NOT fairness; NOT safetyNOT generalization; NOT probability truth