[SOLVED] MATLAB: Corr Function not working for Spearman

MATLAB: Corr Function not working for Spearman

The Code

Rm = corr(timeModel, 'Type', 'Spearman');

Rm
%First row of Rm contains the correlation coefficients between the values of avgExcTime and the expected execution times for all the possible values of KEY3:0
Rc = Rm(1,2:17);
%The entry of Rc with the highest positive value corresponds to the guessed
%key (the first entry of Rc is 1 and corresponds to the autocorrelation of
%avgExcTime, therefore is discarded)
[corr,idx] = max(Rc);
guessedKeyNibble = idx-1```

The error

Index in position 1 is invalid. Array indices must be positive integers or logical values.

Error in Part3 (line 60) Rm = corr(timeModel, 'Type', 'Spearman'); ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^```

What can fix this? The TimeModel has a size of 16 x 17 which is correct and I am really lost as to what is going wrong here?

Solution

It looks like you've encountered a naming conflict with MATLAB's built-in corr function. Here's what's happening and how you can fix it:

The Issue

You likely executed a line similar to:

[corr, idx] = max(Rc);

By assigning the output to a variable named corr, you shadow MATLAB's built-in corr function. As a result, any subsequent calls to corr(...) are interpreted as attempts to index into your variable corr rather than calling the function.

How to Fix It

Clear the Conflicting Variable

Remove the corr variable from your workspace to restore access to the built-in function:
```
clear corr
```
Use a Different Variable Name

To prevent this issue from happening again, choose a variable name that doesn't conflict with MATLAB's built-in functions. For example:
```
[maxCorr, idx] = max(Rc);
```
Now, you can safely use the corr function without any conflicts:
```
R = corr(data1, data2);
```

Best Practices

Avoid Using Names of Built-in Functions: Always check MATLAB's documentation to ensure your variable names don't clash with existing functions.
Use Descriptive Variable Names: Instead of generic names like corr, use more descriptive names such as maxCorrelation or correlationValue to enhance code readability and maintainability.

Summary

By clearing the conflicting variable and choosing a unique name for your variables, you can prevent overshadowing built-in functions and ensure your code runs smoothly.

Hope this helps! Let me know if you have any more questions.