Unexpected MATLAB Operator ':'

I have created a MATLAB Function that I want to be able to read a table that contains the name of Hardware (Column1), Instruction (Column2), and Step (Column3). Each Row represents and instruction for a piece of hardware. The table containing these instructions is in the base workspace and after loading it using evalin to a variable 'x' I want to iterate through each row so I can output the instructions for each piece of hardware accordingly. However when using the ':' operator to interact with the table I receive a "Unexpected MATLAB operator ':' " error. I can index a table using x(1,1) (row 1 column 1) but not by using x(:,1) (all contents of column 1) which worked on the same table in a MATLAB script. Here is the MATLAB script that runs and is what I want to do:

contents = evalin("base","commandSequence");
header = {'Hardware' 'Instruction' 'Step'}
contents.Properties.VariableNames = header;
disp(contents)
Step = 1;
for iRow = 1:Step:height(contents)
    hardware1 = contents{iRow,'Hardware'};
    hardware = string(hardware1);
    
    switch(string(hardware))
        case 'Contactor1'
            Instruction = contents{iRow,"Instruction"};
            Step = contents{iRow,"Step"};            
            
        case 'Contactor2'
            Instruction = contents{iRow,"Instruction"};
            Step = contents{iRow,"Step"};
            
        case 'Contactor3'
            Instruction = contents{iRow,"Instruction"};
            Step = contents{iRow,"Step"};
            
        case 'Voltage'
            Instruction = contents{iRow,"Instruction"};
            Step = contents{iRow,"Step"};
    end
end

Any idea what I'm doing wrong and how I can implement something similar in a MATLAB Function block?

[Image Analyst]

I don't see the colon except in the "for" line, and that looks okay. Can you give us the error message (ALL the red text) so we can see the actual line of code that threw the error. Also attach contents in a .mat file

contents = evalin("base","commandSequence"); % Get contents from the base workspace (probably not good coding practice though).
% Now save it for the Answers forum
save('answers.mat', 'contents');

Attach answers.mat with the paperclip icon.

If none of your cases are met, then Instruction and Step are not assigned and that will cause errors later. Your last case should be "otherwise" instead of "case 'Voltage'".

[Rhett Green]

Code inside MATLAB Function:

function [Contactor1, Contactor2, Contactor3, Voltage1] = fcn()

coder.extrinsic('evalin', 'height');

contents = evalin("base","commandSequence");

header = {'Hardware' 'Instruction' 'Step'}

contents.Properties.VariableNames = header;

disp(contents)

Step = 1;

for iRow = 1:Step:height(contents)

hardware1 = contents{iRow,'Hardware'};

hardware = string(hardware1);

switch(string(hardware))

case 'Contactor1'

Contactor1 = contents{iRow,"Instruction"};

Step = contents{iRow,"Step"};

case 'Contactor2'

Contactor2 = contents{iRow,"Instruction"};

Step = contents{iRow,"Step"};

case 'Contactor3'

Contactor3 = contents{iRow,"Instruction"};

Step = contents{iRow,"Step"};

case 'Voltage'

Voltage1 = contents{iRow,"Instruction"};

Step = contents{iRow,"Step"};

end

end

Errors:

Attempt to extract field 'Properties' from 'mxArray'. Function 'MATLAB Function' (#25.190.198), line 6, column 1: "contents" Launch diagnostic report.

Component:MATLAB Function | Category:Coder error

Colon operands must be all the same type, or mixed with real scalar doubles. Function 'MATLAB Function' (#25.277.293), line 9, column 19: "height(contents)" Launch diagnostic report.

Component:MATLAB Function | Category:Coder error

Cell contents reference from a non-cell array object. Function 'MATLAB Function' (#25.310.335), line 10, column 17: "contents{iRow,'Hardware'}" Launch diagnostic report.

Component:MATLAB Function | Category:Coder error

Undefined function or variable 'hardware1'. The first assignment to a local variable determines its class. Function 'MATLAB Function' (#25.359.368), line 11, column 23: "hardware1" Launch diagnostic report.

Component:MATLAB Function | Category:Coder error

Undefined function or variable 'hardware'. The first assignment to a local variable determines its class. Function 'MATLAB Function' (#25.394.402), line 14, column 19: "hardware" Launch diagnostic report.

Component:MATLAB Function | Category:Coder error

Cell contents reference from a non-cell array object. Function 'MATLAB Function' (#25.456.484), line 16, column 26: "contents{iRow,"Instruction"}" Launch diagnostic report.

Component:MATLAB Function | Category:Coder error

Cell contents reference from a non-cell array object. Function 'MATLAB Function' (#25.505.526), line 17, column 20: "contents{iRow,"Step"}" Launch diagnostic report.

Component:MATLAB Function | Category:Coder error

Cell contents reference from a non-cell array object. Function 'MATLAB Function' (#25.592.620), line 21, column 26: "contents{iRow,"Instruction"}" Launch diagnostic report.

Component:MATLAB Function | Category:Coder error

Cell contents reference from a non-cell array object. Function 'MATLAB Function' (#25.641.662), line 22, column 20: "contents{iRow,"Step"}" Launch diagnostic report.

Component:MATLAB Function | Category:Coder error

Cell contents reference from a non-cell array object. Function 'MATLAB Function' (#25.728.756), line 25, column 26: "contents{iRow,"Instruction"}" Launch diagnostic report.

Component:MATLAB Function | Category:Coder error

Cell contents reference from a non-cell array object. Function 'MATLAB Function' (#25.777.798), line 26, column 20: "contents{iRow,"Step"}" Launch diagnostic report.

Component:MATLAB Function | Category:Coder error

Cell contents reference from a non-cell array object. Function 'MATLAB Function' (#25.859.887), line 29, column 24: "contents{iRow,"Instruction"}" Launch diagnostic report.

Component:MATLAB Function | Category:Coder error

Cell contents reference from a non-cell array object. Function 'MATLAB Function' (#25.908.929), line 30, column 20: "contents{iRow,"Step"}" Launch diagnostic report.

Component:MATLAB Function | Category:Coder error

Errors occurred during parsing of MATLAB function 'CommandParsing1/MATLAB Function'

Component:MATLAB Function | Category:Coder error

Simulink cannot determine sizes and/or types of the outputs for block 'CommandParsing1/MATLAB Function' due to errors in the block body, or limitations of the underlying analysis. The errors might be inaccurate. Fix the indicated errors, or explicitly specify sizes and/or types for all block outputs.

Component:MATLAB Function | Category:Coder error

Simulink cannot determine sizes and/or types of the outputs for block 'CommandParsing1/MATLAB Function' due to errors in the block body, or limitations of the underlying analysis. The errors might be inaccurate. Fix the indicated errors, or explicitly specify sizes and/or types for all block outputs.

Component:Simulink | Category:Block error

[Rhett Green]

Also you noted that using evalin is not wise. Why is that? I initially was reading in an excel file containg the table, but someone mentioned not to read in a non changing table continously in a MATLAB Function. The whole purpose of this block is to read in a Command Sequence matrix/table/file (whatever best works with simulink in external mode), and parse out the instructions to the rest of the model. If there is some block I can simply plug into my model that can easily feed the model a matrix in external mode I could use that but all the From Workspace blocks did not work.

Answer 1

[Rhett Green]

It turns out the issue had something to do with the way I was inputing the file to the MATLAB Function. I was able to fix it by inputing the data as a numerical matrix parameter. I went to "Ports & Data Manager" and changed the scope of the workspace variable from "Input" to "Parameter". I was then able to pass it in by:

function [Contactor1, Contactor2, Contactor3, Voltage1] = fcn(commandSequence)

The matrix had to be numerical (commandSequence) and I was then able to perform the for loop the way I had it.