Using embedded function block to find differential

Question

Amir Khan 2012-7-12

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/43441-using-embedded-function-block-to-find-differential

Hello,

I have a signal and I want to write a code in embedded matlab function block, which could take signal value at the next time step and subtract previous value from it, but the first value has to be zero always. For example, consider the following data with "B" as the main signal, and "dB" would be my required result:

B= 1 3 7 9 11 12

dB= 0 (3-1) (7-3) (9-7) (11-9) (12-11) = 0 2 4 2 2 1

I have written a code to achieve this which is as follows:

function dB=fcn (B)
persistent Bprev;
if isempty (Bprev)
Bprev=B;
end
dB=B-Bprev;

The results from this function, for the same values of B are as follows: # B=1 3 7 9 11 12 # dB= 0 2 6 8 10 11

I think my code is retaining all the previous dB values and adding them to the next dB values. i.e dB= Bnext-Bprev+dBprev, whereas I only want the function to do like this dB= 0 (first value) and then Bnext-Bprev

Can somebody help me in sorting this out.. Will greatly appreciate any help! Thanks

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

TAB 2012-7-12

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/43441-using-embedded-function-block-to-find-differential#answer_53320

编辑：TAB 2012-7-12

在 MATLAB Online 中打开

As per your requirement

function dB=fcn(B)
   persistent Bprev;
   if isempty (Bprev)
      Bprev = B;
      dB = 0;
   else
      dB = B-Bprev;
      Bprev = B; % Save current value to use it as previous in next sample time. 
   end