NNPREDICT directive

Forms predictions from a multi-layer perceptron neural network fitted by NNFIT.

Option

PRINT = string tokens	Controls fitted output (description, predictions); default desc, pred

Parameters

X = pointers	Input variates
PREDICTIONS = variates	Predictions
SAVE = pointers	Details of the network

Description

NNPREDICT forms predictions using a neural network fitted by NNFIT. The type of neural network fitted by NNFIT is a fully-connected feed-forward multi-layer perceptron with a single hidden layer. This network starts with a row of nodes, one for each input variable (i.e. x-variate), which are all connected to every node in the hidden layer. The nodes in the hidden layer are then all connected to the output node in the final, output layer.

Details of the fit and the structure of the neural network must be supplied using the SAVE parameter. This must have been saved using the SAVE parameter of NNFIT. If this is not set, the output is from the most recent network fitted by NNFIT. The values of the input variates to be used to calculate the predictions are supplied, in a pointer, using the X parameter. The variates in the pointer must be in exactly the same order as the equivalent variates in the pointer defined for the X parameter in the original NNFIT command.

The output is controlled by the PRINT option, with settings:

description	a description of the network (number of input variables, nodes etc.),
predictions	predicted values.

Option: PRINT.

Parameters: X, PREDICTIONS, SAVE.

Method

NNPREDICT uses the function nagdmc_predict_mlp from the Numerical Algorithms Group’s library of Data Mining Components (DMCs).

See also

Directives: NNDISPLAY, NNFIT.

Commands for: Data mining.

Example

" Example NNPR-1: Forms predictions from a multi-layer perceptron neural 
  network fitted by NNFIT."

" This example predicts the values at the means of the data, after using 
  NNFIT to fit a multi-layer perceptron neural network with five hidden layers, 
  a hyperbolic activation function in the hidden layer and a linear activation 
  function in the output layer."

" The data are in a file called iris.GSH and contain the data from Fisher's
  Iris data set."

SPLOAD   [PRINT=*] '%GENDIR%/Data/iris.GSH' 
POINTER  [VALUES=Sepal_Length,Sepal_Width,Petal_Length,Petal_Width] Measures
CALC     yval = NEWLEVELS(Species)
NNFIT    [PRINT=description,estimates,summary; NHIDDEN=5;\ 
          HIDDENMETHOD=hyperbolictangent; OUTPUTMETHOD=linear; SEED=12]\ 
           Y=yval; X=Measures

VARI     [NVAL=1] vmeasures[1...4]
CALC     vmeasures[]$[1] = MEAN(Measures[])

NNPREDICT [PRINT = desc, pred] X=vmeasures; PRED=p1