How to set patternnet to get the posterior probabilty sum to unity?

I've a 2-class problem and I want the posterior probability of output to sum to 1. Hence, I'm using 'softmax' transfer function for the output layer. Here's my code.

    net = patternnet(10);
    net.divideParam.trainRatio = 80/100;
    net.divideParam.valRatio = 20/100;
    net.layers{2}.transferFcn = 'softmax';

    [net, tr] = train(net, trainInputs, trainTargets);
    testOutputs = net(testInputs);

    disp(testOutputs')

The sum of the output values exceed 1 though. I must be missing something. Please help. Thanks.

Answer 1

[Greg Heath]

help nndataset % Choose classification/pattern-recognition data with 2 classes

 close all, clear all, clc
for k=1:4
    if k==1
        [x,t] = crab_dataset;
    elseif k==2
        [x,t] = glass_dataset;
    elseif k==3
        [x,t] = cancer_dataset;
    elseif k==4
        [x,t] = ovarian_dataset;
    end

    [ I N ]      = size(x)
    [ O N ]      = size(t)
    check1(k)    = max(abs(sum(t)-ones(1,N)))
    net          = patternnet(10);
    [ net tr y ] = train(net,x,t);
    check2(k)    = max(abs(sum(y)-ones(1,N)))
end

%check1 = 0 0 0 0

%check2 = 2.2204e-16 * ones(1,4)