Hi Sunita,
I understand that you want to know how R is calculated for a multiple output ANN(Artificial Neural Network). The formula for calculating the R value is provided in the following documentation:
The R value for multiple outputs can be calculated as follows (where y_predicted and y_actual will be matrices):
% Sum of squared errors
SSE = sum((y_predicted - y_actual).^2,"all")
% Total sum of squares
SST = sum((y_actual - mean(y_actual)).^2,"all");
% Normalized Mean Square Error
NMSE = SSE/SST
% R squared
Rsquared = 1 - NMSE
You may also refer to this MATLAB answer for MSE calculation for multiple output neural network :
