matlab and Octave 笔记

matlab and Octave 笔记
- 数据类型
  - 内建数据类型

数据类型

: typeinfo()

返回当前安装的所有数据类型

: typeinfo (expr)

返回expr的类型

typeinfo return| example

|- cell | {1, 2} scalar | 1
1.0 complex scalar | i
j
1+1j matrix | [1, 2] diagonal matrix | eye(3) complex matrix | [1j, 1j] bool [matrix] | true, false complex diagonal matrix range | 1:10, 1:2:10 string | “abc” sq_string | ‘abc’ int8 [scalar, matrix] | int8(10) int16 [scalar, matrix] | int16(10) int32 [scalar, matrix] | int32(10) int64 [scalar, matrix] | int64(10) uint8 [scalar, matrix] | uint8(10) uint16 [scalar, matrix] | uint16(10) uint32 [scalar, matrix] | uint32(10) uint64 [scalar, matrix] | uint64(10) sparse bool matrix sparse matrix sparse complex matrix struct | s.name = ‘wang’; s.age = 19;
s = struct ()
s = struct (field1, value1, field2, value2, …)
s = struct (obj) class cs-list magic-colon built-in function user-defined function dynamically-linked function function handle | f = @sin float scalar float complex scalar float matrix float diagonal matrix float complex matrix float complex diagonal matrix permutation matrix null_matrix | [] null_string | “” null_sq_string | ‘’ lazy_index onCleanup octave_java object

内建数据类型

graph LR
    datatype[Built-in Data Types]
    datatype --> numeric
    numeric --> float & integer
    float --> double & single
    integer --> int8["(u)int8"] & int16["(u)int16"]
    integer --> uint32["(u)int32"] & uint64["(u)int64"]
    datatype --> logical
    datatype --> char

: classname = class (obj)

% class(obj)
>> a = 123
>> class(a)
ans = double

判断对象类型

% isa(obj, classname)
>> a = 123
>> isa(a, 'double')
ans = 1
>> isa(a, 'float')
ans = 1
>> isa(a, 'numeric')
ans = 1

值类型转换

: cast (val, “type”)

将val转换为type类型

% type: "double", "single", "logical", "char", "int8", "int16", 
%       "int32", "int64", "uint8", "uint16", "uint32", "uint64" 

类型转换

: y = typecast (x, “class”)

将x在内存中值映射为class类型.

>> x = uint16 ([1, 65535]);
>> typecast (x, "uint8")
ans =
    1    0  255  255

大小端转换

: swapbytes (x)

>> swapbytes( uint16(1:4))
ans =
   256   512   768  1024

最大值, 最小值, 和相对精度值

realmax, realmin, eps

NA(Not Available) 值

: NA

: NA (n)

: NA (n, m)

: NA (n, m, k, …)

: NA (…, class)
class: “double” or “single”.

判断NA值

: isna(x)