how to create and store a matrix from a dataset comprising of certain rows from the dataset.

Need to create a matrix from a dataset that selects certain rows depending on whether a given condition is fulfilled. For eg, from the IRIS dataset, create a matrix comprising of first 30 samples for each class.

Answer 1

[KSSV]

load iris.dat               
setosa = iris((iris(:,5)==1),:);        % data for setosa
versicolor = iris((iris(:,5)==2),:);    % data for versicolor
virginica = iris((iris(:,5)==3),:);     % data for virginica
obsv_n = size(iris, 1);                 % total number of observations

[Apurva Jariwala]

Thanks for the response, i have written the following code to divide the iris dataset into training and testing dataset. Any help to reduce the lines of code is appreciated

setosa = Tnew((Tnew(:,5)==1),:); %Tnew is the iris dataset

Ttest1 = setosa(1:40,:);

Ttrain1 = setosa(41:50,:);

versicolor = Tnew((Tnew(:,5)==2),:);

Ttest2 = versicolor(1:40,:);

Ttrain2 = versicolor(41:50,:);

virginica = Tnew((Tnew(:,5)==3),:);

Ttest3 = virginica(1:40,:);

Ttrain3 = virginica(41:50,:);

Ttest = [Ttest1; Ttest2; Ttest3];

Ttrain = [Ttrain1; Ttrain2; Ttrain3];