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# How to access specific data when using "getfield"

Asked by Artu on 27 Jun 2012

Hello all,

I am using the following code to analyse some data stored in a structure:

```for i=1:10;
mean_value (i) = mean(getfield(Charge,strcat('Curve',int2str(i))));
end
```

"Charge" is the name of the structure, and "Curve" is each one of the 10 array of data inside it. So for this example, I get a vector with 10 elements that shows the average value of each group of data (the structure contains 10x(8670x1) elements). Now I want to take only the first 1416 elements of each array and to get its mean value. But I don't know how to do this.

Any suggestion? Thanks you so much!

Best regards.

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Answer by Kye Taylor on 27 Jun 2012

If I understand your question, this may work...

```for i=1:10;
myData(:,i) = getfield(Charge,strcat('Curve',int2str(i)));
end
```
```mean_value = mean(myData);
meanValueFirstBunch = mean(myData(1:1416,:));
```

Answer by Leah on 27 Jun 2012

You can reference the field of a structure dynamically with Charge.Curve1 or Charge.('Curve1') Loren has some nice blog posts on structures http://blogs.mathworks.com/loren/2009/05/20/from-struct-to-dataset/

```i=0
for fname=fieldnames(Charge)'
i=i+1;
mean_value(i)=mean(Charge.(char(fname))(1:1416));
end
```

## 1 Comment

Jan Simon on 27 Jun 2012

fname{1} is more efficient than char(fname).

Answer by Walter Roberson on 27 Jun 2012

for i = 1 : 10 mean_value(i) = mean(Charge.(str2num(i, 'Curve%d'))); end