How can I add a trendline to a scattergraph of multiple data sets?

Hey Everyone,

I have uploaded my code and a data set that I am trying to process.

So I created a code that works well enough for my purposes. The trouble that I am having is that I need a scatter graph, with all the points that i included in the plotting section. But i also need a trendline for each plot within that one graph. And I need to find the gradient of the trendline for each data set and store it in a variable.

I tried to use, this command, but i am not sure if it the same as a trendline in excel and also cannot get the gradient for this. I would appreciate any help!!

lsline

Answer 1

[Star Strider]

The lsline function needs a bit of help to give up its secrets.

Try this:

figure
scatter(rand(1,10), rand(1,10))
hold on
scatter(rand(1,20), rand(1,20))
hold off
h = lsline;
for k = 1:numel(h)
    B = polyfit(h(k).XData, h(k).YData,1);
    slope(k) = B(1);
    intercept(k) = B(2);
end

Experiment with your own data and plots to get the result you want.

[Lala0099]

Thank you!

What is the k variable?

[Star Strider]

My pleasure!

The ‘k’ is the loop index. (It can be any legal variable name.) See the documentation on the for function for an introduction to for loops in MATLAB.

[Lala0099]

i implemented it in my code and it does not work

it keeps coming up with :No appropriate method, property, or field 'ccData' for class 'matlab.graphics.primitive.Line'.

[Star Strider]

My example code ran for me without error in R2019b.

What version/release of MATLAB are you using?

Please post your code (and attach any necessary data files) so that I can see what the problem could be.

[Lala0099]

I have attached them in a zip file inthe question. I use 2018 version i think.or maybe 2017

[Star Strider]

I do not see any attachments.

[Lala0099]

Hey sorry, i did attach it but for some reason it did not upload it. I tried to upload the files again, zipped them, but it did not allow me.

So I only uploaded the matlab file.

The table tha i am using is just massive with several sheets, and have loads of data points.

[Lala0099]

I gave it another go and it worked now ! Sorry for the confusion!! I very appreciate your help! Thank you!

[Star Strider]

As always, my pleasure!

[Sena]

Hello, I wanted to do the same thing and used your code.

How to I tweak this code so it is using my data points? Everytime I try to add it into the line, B = polyfit(h(k).XData, h(k).YData,1); with dot indexing it does not work, it gives me this error:

Unrecognized method,

property, or field

'VariableName' for class

'matlab.graphics.primitive.Line'.

[Star Strider]

@Sena — I would have to know more about your particular problem. I just tested it again using R2023b and it still works.