Plotting data from struct

Hi,

I am plotting data from a struct, for example

plot(someStruct.a, someStruct.c)

The figure I obtain I can hardly see my data points. They are tiny dots of different colours when I write;

plot(someStruct.a, someStruct.c,'o-')

It seems to treat the data one by one and does not plot them all as instructed in code. Any idea how to make MATLAB plot the data above with one type of style, colour and size?

[Lizan]

And it doesn't seem to plot the correct numbers for example

someStruct.a = 
1
2
3

someStruct.c

-0.3
-0.6
-0.8

It seems as if the points (1,-0.3), (2,-0.6) and (3,-0.8) does not appear but instead (1,-0.8) and so on?

Answer 1

[Michael Haderlein]

If you have something like you suggest to have:

 someStruct.a=1:10;
 someStruct.c=rand(1,10);
 plot(someStruct.a,someStruct.c)

then it's just working. However, I guess you have something different. Is someStruct an array and a,c just one scalar? I mean something like this:

 someStruct(1).a=1;
 someStruct(2).a=2;
 someStruct(3).a=3;
 someStruct(1).c=1;
 someStruct(2).c=2;
 someStruct(3).c=5;
 plot(someStruct.a,someStruct.c)

There you can't see a lot. In this case, the solution is simply

 plot([someStruct.a],[someStruct.c])

[Lizan]

This solved the problem;

plot([someStruct.a],[someStruct.c])

Thank you!

[Hasti Yavari]

This was the answer to my question too. However I don't understand the solution. Why does this allow me to plot the struct and not just the dot?

[Steven Lord]

In this case when you type:

plot(someStruct.a, someStruct.c)

you're passing six inputs into plot, not two. You can see this more clearly by displaying the size of each input to a function. [In this case, displayAllInputs takes the place of plot.]

fh = @(x) fprintf('Input argument is of size %s.\n', mat2str(size(x)));
displayAllInputs = @(varargin) cellfun(fh, varargin);

Now let's build the non-scalar struct array.

someStruct(1).a=1;
someStruct(2).a=2;
someStruct(3).a=3;
someStruct(1).c=1;
someStruct(2).c=2;
someStruct(3).c=5;

When you call it without the square brackets, you'll see that displayAllInputs is called with six inputs.

displayAllInputs(someStruct.a, someStruct.c)

When you call it with the square brackets, you'll see that displayAllInputs is called with two inputs.

displayAllInputs([someStruct.a], [someStruct.c])

For more information read about comma-separated lists on this documentation page.

Answer 2

[Iain]

 plot(someStruct.a, someStruct.c,'k-o')

That's the answer to the question you're asking.

I suspect that ACTUALLY, you want this:

 plot(someStruct.a', someStruct.c','k-o')

[Lizan]

With

someStruct.c'

I get "Error using ' Too many input arguments".