Undefined function or variable 'activations'

Please sort out this problem. I found this problem in the code given below

function W_CNN=cnnFeatures_newnew(I)

net = load('imagenet-vgg-verydeep-19.mat');

net = vl_simplenn_tidy(net);

beta=0.2; % constant used in exposure mask calculation

for ii=1:size(I,4)

%fetaure extraction from first layer

features(:,:,:,ii) = activations(net,I(:,:,:,ii),1);

Answer 1

[madhan ravi]

suspect activations hasn‘t been defined nor is a function , check it

whos activations % to see if a variable
which activations -all % to see if a function