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Mathematical Operators

20 一月, 2016 - 09:21

The evaluation of expressions is accomplished with arithmetic operators as we use them in scientific calculators. Note the addtional operators shown in the table below:

Table 2.1 Operators

Operator

Name

Description

+

Plus

Addition

-

Minus

Subtraction

*

Asterisk

Multiplication

/

Forward Slash

Division

\

Back Slash

Left Matrix Division

^

Caret

Power

.*

Dot Asterisk

Array multiplication (element-wise)

./

Dot Slash

Right array divide (element-wise)

.\

Dot Back Slash

Left array divide (element-wise)

.^

Dot Caret

Array power (element-wise)

 

NOTE: The backslash operator is used to solve linear systems of equations, see Linear Equations .

IMPORTANT: Matrix is a rectangular array of numbers and formed by rows and columns.

For example A=\bigl(\begin{smallmatrix} 1 & 2 & 3 & 4\\ 5 & 6 & 7 & 8\\ 9 & 10& 11 &12 \\ 13& 14 & 15 &16 \end{smallmatrix}\bigr) . In this example A consists of 4 rows and 4 columns and therefore is a 4x4 matrix. (see Wikipedia 1).

IMPORTANT: Row vector is a special matrix that contains only one row. In other words, a row vector is a 1xn matrix where n is the number of elements in the row vector. B=\bigl(\begin{smallmatrix} 1 2 3 4 5 \end{smallmatrix}\bigr)

IMPORTANT: Column vector is also a special matrix. As the term implies, it contains only one column. A column vector is an nx1 matrix where n is the number of elements in the column vector. C=\bigl(\begin{smallmatrix} \\ 1 \\ 2 \\ 3 \\ 4 \\ 5 \end{smallmatrix}\bigr)

NOTE: Array operations refer to element-wise calculations on the arrays, for example if x is an a by b matrix and y is a c by d matrix then x.*y can be performed only if a=c and b=d. Consider the following example, x consists of 2 rows and 3 columns and therefore it is a 2x3 matrix. Likewise, y has 2 rows and 3 columns and an array operation is possible.\textrm{x}=\bigl(\begin{smallmatrix} 1 & 2 &3 \\ 4&5 &6 \end{smallmatrix}\bigr) \textrm{ and y }=\bigl(\begin{smallmatrix} 10 & 20 & 30\\ 40& 50 &60 \end{smallmatrix}\bigr) \textrm{ then x.*y}=\bigl(\begin{smallmatrix} 10 & 40 & 90\\ 160& 250 &360 \end{smallmatrix}\bigr)