App Designer charting issue with data not linking

Question

Nathaniel Johnston 2021-2-13

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/744152-app-designer-charting-issue-with-data-not-linking

回答： Jacob Mathew 2024-2-28

Hi

I am wondering if someone would be able to steer me in the right direction, currently I am trying to build a UI for charting i have created my data base and connected it to matlab from MySQL workbench and it is showing data which is great and when I type it is showing the variable and it is in the workspace too.

My current issue is trying to get the data to plot in a graph in app designer it doesn't seem to be able to reference the data it is saying it can't resolve the issue or dot indexing isn't supported.

I have code in the start up function

This is the code I have in

datasource = 'namedata';

username = 'user';

password = 'pass';

query = ['SELECT * ' ...

'FROM namedata.players'];

data = query;

plot(app.UIAxes,[data.Weight_kg]);

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Jacob Mathew 2024-2-28

After reading through your question, there is limited data available to fully grasp your query. Suggest that you share the code, dataset, and the error you are facing at which line of the code to help solve the issue further.

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Answer 1

Jacob Mathew 2024-2-28

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/744152-app-designer-charting-issue-with-data-not-linking#answer_1417756

With the limited context provided, a workaround could be to identify what datatype the variables are. Datatypes like array or cell array cannot be accessed using the dot operator and instead requires the use of parenthesis i.e () and curly braces i.e {} respectively. The documentation below showcases some examples of using these:

https://www.mathworks.com/help/releases/R2020b/matlab/math/array-indexing.html?searchHighlight=array%20indexing&s_tid=doc_srchtitle

https://www.mathworks.com/help/releases/R2020b/matlab/matlab_prog/access-data-in-a-cell-array.html?searchHighlight=Access%20Data%20in%20Cell%20Array&s_tid=doc_srchtitle

Further, please ensure that the SQL Query is being executed before being stored in the variable data. Refer to how to use SQL in MATLAB in the below documentation:

https://www.mathworks.com/help/releases/R2020b/database/sql-prepared-statements.html?searchHighlight=sql&s_tid=doc_srchtitle