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Error using findpeaks Expected Y to be one of these types: double, single Instead its type was table.

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Hi,
I am trying to read a file and find its peak. But the findpeak function keeps throwing errors. Please help. I am new to matlab.
%clear,clc
readtable('KD.xlsx');
x=qw(:,1);
y=qw(:,2);
%y=data(:,2');
Peaks=findpeaks(ans);
[pks,locs] = findpeaks(KD);
plot(x,y,y(locs),pks,'or')
xlabel('Xvalue')
ylabel('Peak')
axis tight
error message:
Error using findpeaks
Expected Y to be one of these types:
double, single
Instead its type was table.
Error in findpeaks>parse_inputs (line 199)
validateattributes(Yin,{'double','single'},{'nonempty','real','vector'},...
Error in findpeaks (line 136)
= parse_inputs(isInMATLAB,Yin,varargin{:});
Error in Untitled (line 6)
Peaks=findpeaks(ans);

  2 Comments

Walter Roberson
Walter Roberson on 16 Jan 2021
You have a clear at the top of your code. Where are you expecting the array qw to be pulled out of?
Peaks=findpeaks(ans);
I recommend against relying on the value of ans in programming. Someone (you, later in time) should not have to know that inserting additional statements that do not modify existing variables could end up changing the meaning of the code because they happen to change ans.

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Accepted Answer

Cris LaPierre
Cris LaPierre on 16 Jan 2021
Best to use variable you define rather than ans.
The function readtable returns a table. Each column of a table is, in turn, a variable. So a table is made up of variables.
The input for findpeaks must be a variable, but you are passing in the entire table. The error will be fixed if you can instead pass in a variable.
See this page for how to access data in a table. Any of the syntaxes that return an array are what you need. If you know the variable name, the simplest is to use dot notation.
Peaks=findpeaks(Tname.Varname);

  7 Comments

Show 4 older comments
Venkatakrishnan Rengarajan
I understand the variable assignment. However, the problem still persists. I copied the modified code of yours and ran again. It did not help. I tried many iterations.
Peak
Error using findpeaks
Too many output arguments.
Error in Peak (line 4)
[pks,locs] = findpeaks(y);
This is the error now. Maybe I should access the signal acquistion toolbox and put that in the path. Thanks a lot for taking your time to help me. I really appreciate it.
Venkatakrishnan Rengarajan
I just realized that, before starting this problem, I downloaded a set of functions from a university website. It had findpeaks command in it. The input in that command was different compared to the default "findpeak" command in the signal processing toolbox. After I deleted the my downloaded package (i just changed the file path, tbh), it worked perfectly.
Thanks for all the comments and help. I really appreciate it.

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