Indexing error message that makes no sense with cfit

Hi y'all,

I'm trying to fit a polynomial to some data, and I keep on getting an indexing error message which makes no sense. Perhaps one of you can see the forest for the trees. Here's an example of the data:

r =

   23.6406    2.8430
   16.8598    1.9837
   10.8369    1.2979
    6.8227    1.0700
   15.3950    1.8485
   17.8152    2.5149
   21.3562    4.4245
   23.5249    2.7839
   27.0158    1.6553
   24.3364    3.1090
   21.7304    2.3873
   15.4503    1.3488
   21.8857    1.9761
   28.4438    8.2376
   17.5644    7.2797
   14.6695    4.7655
   24.3061    1.9693
   24.2177    3.8884
   26.6174    2.3952
   26.3180    8.7369
   19.6436    5.7631
   -4.3673    1.1343
    1.9130    0.5210
    9.9632    6.3485
   16.6363    4.9399
   14.4421    3.3374

but when I try and fit it I get an indexing error message which makes no sense:

f=fit(r(:, 1), r(:, 2),'poly2')
Subscript indices must either be real positive integers or logicals.

I don't see how this can be an indexing issue, as I can index to plot the full dataset:

figure, plot(r(:, 1), r(:, 2), '.')

Any ideas? I've even re-started matlab as it does sometimes get buggy when I've had it open for a while, but no dice.

Thanks!

Answer 1

[Star Strider]

My guess is that the error refers to fit, and MATLAB believes it’s an array, not a function. Do you have a previously assigned variable named ‘fit’ that’s ‘overshadowing’ the function name?

Run this from your Command Window or a script:

which fit -all

If the first line in the returned output is:

fit is a variable.

You’ve found the problem. The solution is to name the variable something else.

[Kate]

Nailed it. Very silly mistake on my part, thanks :)

[Star Strider]

As always, my pleasure!

Thanks! (I learned about this from my own very silly mistake.)