I have a gui slider that calls a value from an array that gets the error 'Index in position 2 is invalid. Array indices must be positive integers or logical values.' when trying to update a textbox which causes my gui to not work.

I have attached my code so you can see where it is going on. Line 96 is where the code stops working when trying to update the text with the array indices.

[Geoff Hayes]

Thomas - the slider value need not be an integer...most likely (in this case) it is a float and so trying to use this as index into your array will result in the error. You may want to round up (or down) the slider value before using it to access an element in your array (and also make sure that the rounded value doesn't exceed the dimensions of your array).

[Thomas Firsich]

Would you happen to know if I am able to have two sliders, each with a text box to update? I am wanting to show the values that each slider is at within the array. However, I can only get the first one to update. After trying the round() to get the values to the nearest integer, I am getting "Undefined function or variable 'sl2'.", which makes me think that having a second slider there might not work.

[Stephen23]

"I am getting "Undefined function or variable 'sl2'.", which makes me think that having a second slider there might not work."

You get that error because of a bug in your code, not because MATLAB has restrictions on how many sliders you can put into a GUI.

"Would you happen to know if I am able to have two sliders, each with a text box to update?"

Of course. Take a look at my FEX submission cubehelix_view, which generates multiple sliders in a loop:

https://www.mathworks.com/matlabcentral/fileexchange/43700-cubehelix-colormaps--beautiful--distinct--versatile-

[Geoff Hayes]

Thomas - your code seems to be using the same callback for each slider. Consider using a different callback for each slider (since each performs a slightly different action in terms of which text control gets updated with some data).

[Thomas Firsich]

Yeah that worked, thank you Geoff. I knew it wasn't a problem with MatLab as I am just an amateur coder anyways Stephen. Sorry about the wording.

[Thomas Firsich]

I am getting now just a weird error at certain values of the slider...4,6,7,8,9,etc...I am attaching the error and proof that the slider values are integers before it is passed on to the function.

[Adam]

Those are not necessarily integers, depending how you formatted the output. Normally an integer would not trail a load of 0s unless it has some small error a long way down the decimal places.

You can just use

doc round

if you are happy that the errors are just minor rounding errors rather than something more significantly wrong.