how to generate random data

number of data = 1000; dimension=20; and save in mat format.

[jgg]

What kind of randomness do you want? There are many ways to generate a random variable. For instance, rand(1000,20) will give you a matrix of the desired size that is uniformly distributed on 0 to 1.

[Image Analyst]

What do you mean by dimension=20? Do you mean it's a 1-D vector with a length of 20 elements or 1000 elements, or do you mean a 20-D array with 1000 length of each dimension (in which case you won't have enough memory)?

If you want this:

data = rand(1000, 1000, 1000, 1000, 1000, 1000, 1000, 1000, 1000, 1000, 1000, 1000, 1000, 1000, 1000, 1000, 1000, 1000, 1000, 1000);

then you can't have that and you most likely don't need that.

[fred bnm]

thanks. rand(1000,20) is ok. but how to assign 4 label classes on this.and please say how to plot that data with labels.

[jgg]

I'm not sure what you mean? What kind of labels do you want assigned?

[the cyclist]

How about this, fred? Spend the time to compose a complete, coherent description of what it is that you want as input and output from your program. This isn't twitter; feel free to use more than 140 characters.

Answer 1

[Walter Roberson]

data = rand(1000,4);

If the 4 class labels are to be random and equal probability but not necessarily exactly equal number, then

label = randi(4, 1000, 1);

If the 4 class labels must be equal occurrence then

population = [1 * ones(250,1); 2 * ones(250,1); 3 * ones(250,1); 4 * ones(250,1)];
label = population(randperm(1000));

If you wanted a precise distribution that was not equal numbers, then you could adjust the counts in the population matrix.

Your data is 4 dimensional. You cannot plot 4 spatial dimensions. You can encode the 4th dimension as color, but you need to be careful; see http://blogs.mathworks.com/steve/2014/10/20/a-new-colormap-for-matlab-part-2-troubles-with-rainbows/

pointsize = 20;
scatter3(data(:,1), data(:,2), data(:,3), pointsize, data(:,4));   %4th dimension used as color
colormap(parula);     %needs R2014b or later

And to add the labels:

labstr = cellstr( num2str(label(:)) );
text( data(:,1), data(:,2), data(:,3), labstr );

this is going to be rather crowded...