Error trying to load a file in MATLAB Grader

I'm trying to load an Excel file (one column of numbers) in a MATLAB Grader script and getting an "Error using load" that says, "Number of columns on line 2 of ASCII file NavyData.xlsx must be the same as previous lines." I have no idea how to fix that error, because I don't know what it even means. Any suggestions?

[Geoff Hayes]

William - can you use load with an Excel file (see load filename input parameter)? Why not convert the Excel file into an ASCII text file and try that instead?

[William Stuckey]

That worked, thnx!

Answer 1

[Cris LaPierre]

It depends on what the end task is you are trying to achieve, but my recommendation would be to use readtable.

[Cris LaPierre]

Are you a student solving the problem or an instructor authoring a problem? If the later, I would recommend teaching a workflow that is how one would typically solve the problem. It is my observation that it is not common to convert an *.xlsx file to ascii in order to load it into MATLAB.

[William Stuckey]

I'm a physics professor. I'm not teaching MATLAB, I'm just trying to use it to teach computational physics. When I took computational physics, we used FORTRAN, but my institution has MATLAB. I've never had a course in MATLAB myself, I'm trying to learn it as I go.

[Cris LaPierre]

Let me recommend a couple things to help you get started.

In order to learn the basics of MATLAB, consider going through MATLAB Onramp, a free, self-paced tutorial that should take about a couple hours to complete.

As an instructor, you may also find value in going through the Teaching with MATLAB self-paced course as well. It will introduce you to how MathWorks products can be used in an education setting.

[William Stuckey]

Thnx, I did the Teaching with MATLAB course and I'm creating assignments in MATLAB Grader for my students now (that's where this issue arose). I'm gradually learning more of MATLAB's capabilities as I teach the course (this is my third time through with MATLAB). I'm an old physicist and the computer terminology is very different today than when I was a student (1980-87), so some of the terminology used in online explanations is Greek to me :-)

[Cris LaPierre]

One thing that might help is the example problems that come with MATLAB Grader.

When you create a new problem, you are presented with what we call the problem chooser. There, you will see several tiles. Under the "Sample Problems from MathWorks" is a tile called "Getting Started with MATLAB Grader" (there are several others organized by topics such as Intro to Programming, Numerical Methods, Dynamics, System Dynamics and Controls, etc. If you don't see them but would like access, contact customer support to submit a request. They are free but access is restricted to instructors).

As the title suggests, these problems demonstrate how to accomplish various tasks. The best way to see what problem does what is to look at the table at the very end of the Teaching with MATLAB course. I'd point out these two problems in particular.

• Analysis of stress-strain data. This uses readtable to load a *.xlsx file into the workspace.
• Determine the drag coefficient by fitting a polynomial to velocity-force data. This uses readtable to load a *.csv file into the workspace.

Hopefully these help you. There are extra comments added to some of the assessment tests to explain what is being done.

[William Stuckey]

Thnx very much, Cris!