In nntool, inputs and targets must be numeric matrices (each column = one sample). Your dualout is a cell array, which causes the error. The solutionis to make it a numeric 2×7 matrix, not a cell array.
% Input (2×7)
probx = [1.175 1.675 2.175 2.675 3.175 3.675 4.175;
23.9 23.9 23.9 23.9 23.9 23.9 23.9];
% Target output (2×7)
dualout = [0.640 0.705 0.909 0.671 0.781 0.736 0.440;
1.155 1.096 1.009 1.027 0.899 0.737 1.827];
nntool % now import probx as input, dualout as target
