colon (MATLAB C++ Math Library)

Generate a sequence of indices

C++ Prototype

mwIndex colon();
mwIndex colon(mwArray start, mwArray end);
mwIndex colon(mwArray start, mwArray step, mwArray end);

Arguments

start
Initial value

step
Increment value

end
Final value

C++ Syntax

B = A(colon());
B = A(colon(1,10));
B = A(colon(1,2,10));

MATLAB Syntax

colon = start:stop
colon = start:step:stop

Description

colon() generates a "sequence" of indices. colon() stands for "every value." For example, A(colon()) means every value in array A. A(1,colon()) means every column in the first row.

colon(start, end) generates a vector of (end - start) + 1 elements. The elements in the vector are start, start+1, start+2, , start+n, end. Each element in the vector is one greater than the preceding element. Iteration stops when the start+n is larger than end, yet the last value in the vector is always end. This can decrease the distance between the last two elements to less than 1.

colon(start, step, end) generates a vector of ((end - start)/step) + 1 elements. The elements in the vector are start, start+step, start+(2*step), start+(3*step), , start+(n*step), end. Iteration stops when the start+(n*step) is larger than end, yet the last value in the vector is always end. This can decrease the distance between the last two elements to less than step. Specifying a negative step generates a decreasing sequence. Specifying a sequence that will not terminate raises an exception.