Unrecognized function or variable 'carsmall'

Hello, I'm doing a very basic exercise which starts with importing carsmall.mat dataset and protting its data with gplotmatrix(). Here is the code I wrote:

clear all;
close all;
clc;

%% Initialization
load carsmall.mat;
figure()
gplotmatrix(carsmall');

The problem is that when I run the script I get this output message:

Unrecognized function or variable 'carsmall'.

Error in Exercise_3_1 (line 8)
gplotmatrix(carsmall);

I don't get it. I have the Statistics and Machine Learning Toolbox installed. I'he done the same exercise importing iris_dataset.mat and it all worked fine.

Can anybody please help me? I've also updated anything possible but nothing changed...

Thank you

Answer 1

[John D'Errico]

This is not a question of you updating your version. I can see what you did, but not what you were hoping to do. Suppose I try this:

load randomstuff.mat
Error using load
Unable to read file 'randomstuff.mat'. No such file or directory. 

So, if I try loading a file that does not exist, it gives me an error, telling me the file does not exist, but NOT what you got.

What did you get?

Unrecognized function or variable 'carsmall'.
Error in Exercise_3_1 (line 8)
gplotmatrix(carsmall);

That tells me the load did work, but there is no variable named carsmall in that .mat file.

I would suggest you try this:

load carsmall.mat;
whos
  Name                Size            Bytes  Class     Attributes

  Acceleration      100x1               800  double              
  Cylinders         100x1               800  double              
  Displacement      100x1               800  double              
  Horsepower        100x1               800  double              
  MPG               100x1               800  double              
  Mfg               100x13             2600  char                
  Model             100x33             6600  char                
  Model_Year        100x1               800  double              
  Origin            100x7              1400  char                
  Weight            100x1               800  double      

So there is indeed no variable by that name in the .mat file. Lots of other stuff, but not carsmall. What you want to do next is up to you.

[Alberto Ongaro]

Got it, I guess I was just following too closely the text of the exercise. Point is that in another one I simply did:

clear all;
close all;
clc;
%% Initialization
load iris_dataset.mat;
figure()
gplotmatrix(iris_dataset');

and worked perfectly. Maybe that's because iris_dataset contains just numbers and not characters like carsmall does?

[Walter Roberson]

No it is because iris_dataset happens to contain a variable with the same name and carsmall does not.

[Alberto Ongaro]

No it doesn't, I just tried:

load iris_dataset
whos

% and here is what I get:

Name             Size             Bytes  Class     Attributes

  irisInputs       4x150             4800  double              
  irisTargets      3x150             3600  double              

My guess is that IF the dataset contains just numerical variables belonging to the same class, then we can call gplotmatrix() putting the name of the dataset inside the brackets; otherwise (like in carsmall dataset) we have to extract the desired variables belonging to the same class, place them in a vector, and then we can finally apply gplotmatrix().

[Walter Roberson]

gplotmatrix(iris_dataset');

iris_dataset is a function. In this context it returns the irisInputs variable from iris_dataset . You do not even have to load the dataset first.

My guess is that IF the dataset contains just numerical variables belonging to the same class, then we can call gplotmatrix() putting the name of the dataset inside the brackets;

No, it has nothing ot do with that. It is because iris_dataset is a function that is returning the values.

>> which iris_dataset
/Volumes/T5/T5 Applications/MATLAB_R2020a.app/toolbox/nnet/nndemos/nndatasets/iris_dataset.m

[Alberto Ongaro]

That makes a lot of sense then. Thank you so much!