Error in locating a reference cell for calculations

So far I have got this code:

%%=================================================
%%to find average power first use "find" function to find the first zero in
%%Fz, have the cell referenced
%%then use nanmean for average power(av_pwr)
%%use nanmin for peak power (peak_pwr)
%%=================================================
  ref= find(data{i,1}(:,5)==0);
  ref=ref(1);%returns all times zero occurs then extracts first time data is 0
  peak_pwr(i,1) = nanmin (data {i,1}(1:ref,5)); 
%preak power in coloumn E1 in all data with reference to cell found
  av_pwr(i,1)=nanmean(data{i,1}(1:ref,5));
%average power in coloumn E1 in all data with reference to cell found

I have tried to locate the first zero in column E1 and then use this as a reference cell to get the peak and average power. However it is coming up with this error:

Attempted to access ref(1); index out of bounds because numel(ref)=0.

Error in code (line 53) ref=ref(1);%returns all times zero occurs then extracts first time data is 0

anyone know how to get around this?

Answer 1

[David Sanchez]

If you read the line:

Attempted to access ref(1); index out of bounds because numel(ref)=0.

you can see that

data{i,1}(:,5)==0

is never fulfilled and therefore, ref remains an empty array with no values in it.

When you tried to access its first value:

ref=ref(1)

the system complains (yields an error) because there is nor such an element. Since I do not have data, it is nor easy to tell whether any of its elements equals 0 in any moment.

[Adrienne]

Sorry, I still don't quite understand what is it that I am doing wrong? I've referenced my data set to find all the zeros in the cells, so i want it to reference the cell that has the first data starting at zero. so then i can use the data before that first zero to calc. peak and average power?

[Adrienne]

I now understand that it is just an array of zeros its collecting and so it says its empty but I want find the first cell where it is zero as a reference cell so that I can use all cells up to this to find the peak power and average power from the Fz column. I've attached an example data so it might make it clearer.

[David Sanchez]

the problem is in your data cell array.

In your line

ref= find(data{i,1}(:,5)==0);

who is i ? What's the type of data within data? If they are strings, ref will always be an empty array.

[David Sanchez]

how are you reading the CSV file?

[Adrienne]

(i) is for the loop so that it stores the information rather than write over it each time as I have to know all the data for each 81 jumps. i had trouble reading them in so I had to do it like this:

i=1:njump;
  x=sprintf('Trial%02d.csv',i),sprintf('Trial%02d',i),'A1:E7000';;% jump data
  data{i}=xlsread(x,'A1:E7000');
      % code
end