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Matvec Users’ Guide

Matvec Users' Guide

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3.4. COMPUTATION 31<br />

Col 1 Col 2 Col 3<br />

Row 1 1 0 0<br />

Row 2 4 5 0<br />

Row 3 7 8 9<br />

> A.tril(-1)<br />

triu<br />

Col 1 Col 2 Col 3<br />

Row 1 0 0 0<br />

Row 2 4 0 0<br />

Row 3 7 8 0<br />

A.triu(k) returns the elements on and above the k-th diagonal of A where k is optional. k=0 (default) is the<br />

main diagonal, k ¿ 0 is above the main diagonal and k ¡ 0 is below the main diagonal.<br />

This member function is a user-defined function, it’s loaded automatically into memory whenever you<br />

launch <strong>Matvec</strong>.<br />

For example,<br />

> A = [1,2,3;4,5,6;7,8,9]<br />

Col 1 Col 2 Col 3<br />

Row 1 1 2 3<br />

Row 2 4 5 6<br />

Row 3 7 8 9<br />

> A.triu()<br />

Col 1 Col 2 Col 3<br />

Row 1 1 2 3<br />

Row 2 0 5 6<br />

Row 3 0 0 9<br />

> A.triu(1)<br />

variance<br />

Col 1 Col 2 Col 3<br />

Row 1 0 2 3<br />

Row 2 0 0 6<br />

Row 3 0 0 0<br />

A.variance() returns a vector containing variance values for each column of A.<br />

vec<br />

A.vec(), where A is a matrix, returns a Vector converting from matrix A column-by-column. For example,<br />

> A=[1,2;3,4]<br />

Col 1 Col 2<br />

Row 1 1 2<br />

Row 2 3 4<br />

> A.vec()<br />

i = 1 i = 2 i = 3 i = 4<br />

1 3 2 4

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