Proposal to get TP, FP, FN of all targets

[sathyarr]

Feature description

Proposal to get TP, FP, FN of all targets:

At a certain point, we have three different arrays for all the targets,
tp_sum, pred_sum, true_sum

e.g.,

target_names = ['person', 'org', 'place']
tp_sum   = [1 0 0]
pred_sum = [1 0 1]
true_sum = [1 1 0]

Here, tp_sum is used as numerator of both Precision and Recall calculations.

So, tp_sum is nothing but a collection of True Positive counts of each target.

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pred_sum is being used as denominator of Precision.
As per Precision's definition then, pred_sum == TP + FP

Here, we already know the count of TP (from tp_sum).
To get FP, we shall do, FP = pred_sum - tp_sum

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true_sum is being used as denominator of Recall.
As per Recall's definition then, true_sum == TP + FN

Here, we already know the count of TP again (from tp_sum)
To get FN, we shall do, FN = true_sum - tp_sum

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Does this sound logical?

If so, better to add a function for this, like performance_measure?