How to do wavelet transform in simulink by using Function block?

Hello

i am doing dc motor simulation by using simulink. i want to analyse current signal by wavelet transform theory.

in my case, i use Function block to write the code but it shown some error 'Failed to resolve data 'y' in 'MATLAB Function' to a valid Simulink.Signal object.'

here is my code in function block

function y = fcn(u)

x = u;

level =1;

[c,l] = wavedec(x,level,'db1');

d1 = detcoef(c,l,level);

y= plot(d1)

Anyway, if anyone have some reccommend or some idea to deal with wavelet tranform in simulink(i know, there is a tool called Wavelet Analyzer that able to analyse signal directly. unfortunately, i want to use WT in real-time signal), Please let me know

i am new to matlab and Looking forward to hear from you

Thank you in advance