accessIntervals Function: Subscripting into a Table Using One Subscript Error

Problem Description:

I am working on a MATLAB project involving the Satellite Communications Toolbox. My script uses the accessIntervals function to compute access intervals for satellites and ground stations. However, I consistently encounter the following error:

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Copy code

Subscripting into a table using one subscript (as in t(i)) is not supported. Specify a row subscript and a variable subscript, as in t(rows,vars). To select variables, use t(:,i) or for one variable t.(i). To select rows, use t(i,:).

Steps to Reproduce:

• I created a satellite scenario with the following setup:matlabCopy

codestartTime = datetime(2024, 1, 6, 23, 23, 0);
stopTime = startTime + hours(24);
sampleTime = 60;
sc = satelliteScenario(startTime, stopTime, sampleTime);
sat = walkerDelta(sc, 570e3 + 6378.14e3, 70, 720, 36, 1, ArgumentOfLatitude=15, Name="Starlink");
gs = groundStation(sc, "Name", "Test Station", "Latitude", -35.40139, "Longitude", 148.98167);
ac = access(sat, gs);

• I attempted to call accessIntervals for the Access object:matlabCopy code

Test = accessIntervals(ac(1));

• The error occurs for all Access objects (ac).

Debugging Steps Taken:

• I confirmed the Access objects (ac) are valid and properly initialized:matlabCopy codeAccess Object 1:

Access with properties:

Sequence: [1 721]

LineWidth: 3

LineColor: [0.3922 0.8314 0.0745]

• The error persists for all Access objects.

Questions:

1. Is this a known issue with accessIntervals or the Satellite Communications Toolbox?
2. How can I resolve or work around this error to compute access intervals?
3. Are there alternative methods to compute satellite-ground station access intervals if accessIntervals cannot be used?

Environment: Matlabonline

Answer 1

[Altaïr]

Hi @Bara'ah,

The following code executed in MATLAB Online without any errors:

startTime = datetime(2024, 1, 6, 23, 23, 0);
stopTime = startTime + hours(24);
sampleTime = 60;
sc = satelliteScenario(startTime, stopTime, sampleTime);
sat = walkerDelta(sc, 570e3 + 6378.14e3, 70, 720, 36, 1, ArgumentOfLatitude=15, Name="Starlink");
gs = groundStation(sc, "Name", "Test Station", "Latitude", -35.40139, "Longitude", 148.98167);
ac = access(sat, gs);

Test = accessIntervals(ac(1))

The error Subscripting into a table using one subscript (as in t(i)) is not supported, typically occurs when a table object isn't indexed correctly. The following MATLAB Answer is an example:

https://www.mathworks.com/matlabcentral/answers/1655320

The access function returns a matlabshared.satellitescenario.Access object, not a table. However, the accessIntervals function returns a table object, and indexing it with a single subscript, as shown below, may lead to the error.

Test(1)

For more details on the output types of the access and accessIntervals functions, please refer to these documentation pages:

• access: https://www.mathworks.com/help/aerotbx/ug/matlabshared.satellitescenario.groundstation.access.html
• accessIntervals: https://www.mathworks.com/help/satcom/ref/matlabshared.satellitescenario.access.accessintervals.html