How to create a For loop for a linspace?

I have this code:

    for j = 1:20

      c(j) = linspace(1,10,length(j));

       end

But, the result is a vector "c" with all the values "10":

c= 10 10 10 10 10 10 10....

How can I do to solve the problem? Thnaks

Answer 1

[Star Strider]

Since in every iteration, ‘j’ is a scalar, the length of ‘j’ will always be 1.

I would just use:

c = linspace(1, 10, 20);

or if you actually want varying-length vectors, save ‘c’ as a cell array:

for j = 1:20
    c{j} = linspace(1,10,j);
end

[Michela Longhi]

The problem is that I have to use the linespace in a "scatter" function:

for i = 1:length(temp_discesa_i)

          pause(0.1)
          c = linspace(1, 10, length(temp_discesa_i));
          scatter(temp_discesa_i(i), spazio_discesa_i(i),30,c,'filled')
          pause(0.01);

      end

and Matlab give me an error: "Error using scatter (line 93) CData must be an RGB triplet, an M-by-1 vector of the same length as X, or an M-by-3 matrix."

[Steven Lord]

The loop variable i is a scalar. So you're creating a scatter plot of one point with x=temp_discesa_i(i) and y=spazio_discesa_i(i) each time. In that case, the color input must be an RGB triplet or a scalar that is mapped into the colormap. In order to achieve what I think you want to do with this code, create the linspace vector prior to the for loop and index into c the same way you index into temp_discesa_i and spazio_discesa_i.

But creating a scatter plot for one point at a time seems like a bit of overkill. Are you sure you don't want to simply create a line once and update its XData, YData, MarkerFaceColor, and MarkerEdgeColor properties in the loop? Or would scatter plotting all the data at once be acceptable?

[Star Strider]

@Steven — Thank you.

I am not certain what the objective is. My suggestion is to define the colormap before the loop, as:

c = colormap(jet(length(temp_discesa_i)));

then do the plotting as:

scatter(temp_discesa_i(i), spazio_discesa_i(i),30,c(i,:),'filled')

awaiting further details.

[Michela Longhi]

Yes!!!! It's now working. Thank you to all.

[Star Strider]

Our pleasure!