标题: matlab学习总结 [打印本页] 作者: baqiao 时间: 2021-8-17 15:23 标题: matlab学习总结 h5 {4 f; f# K
一、randn的用法4 J( q9 k$ F x7 C8 g
randn产生均值为0，方差 σ^2 = 1，标准差σ = 1的正态分布的随机数或矩阵的函数。 # P7 z' Z) T& Z! ~用法：: _8 y- h' X& {5 S! \
Y = randn(n)3 m- v( m' r1 d! @! h
返回一个n*n的随机项的矩阵。如果n不是个数量，将返回错误信息。* F' Z6 {$ ]+ |/ F4 T3 o. \; A' ?1 N8 o
Y = randn(m,n) 或 Y = randn([m n]) # G. F( \3 F! `) x$ f6 z
返回一个m*n的随机项矩阵。 - R* b% J+ R9 u0 X- {5 O" aY = randn(m,n,p,...) 或 Y = randn([m n p...]); [( ]5 H( ?) |/ j- M- j
产生随机数组。" I* Q) [2 O7 K' Q( G! V: x
Y = randn(size(A)) 7 T2 d- [8 B7 u% e" E. X- v8 _
返回一个和A有同样维数大小的随机数组。 + i4 S$ b# z0 [! D, `3 c9 Crandn" E0 L4 P% F4 F
返回一个每次都变化的数量。 ; p8 Y! S# D1 v2 V( C! } g; ?7 @s = randn('state'): W9 X/ @, i/ _& N
举例： * ~. M2 h H" c4 W) k4 |' i. i' {9 Q ?; C; u9 A
例 1. R = randn(3,4) 将生成矩阵 + T' n7 T5 Q6 a+ ~( u/ M, } m $ P+ ` p) J0 f, B" L: ER = ( Q# p7 O0 j* ?1.1650 0.3516 0.0591 0.8717* C; u, N( x1 k) @+ z2 q
0.6268 -0.6965 1.7971 -1.4462 + ~6 t) l% e5 E( n0.0751 1.6961 0.2641 -0.7012! m" M# o1 c0 S. b8 l
For a histogram of the randn distribution, see hist. 4 c8 q, J: N" ~; b* x1 C7 Z$ U ! V) E' v- X/ v/ R1 v' m; v例 2. 产生一个随机分布的指定均值和方差的矩阵：将randn产生的结果乘以标准差，然后加上期望均值即可。例如，产生均值为0.6，方差为0.1的一个5*5的随机数方式如下：5 S G1 R* r- Y4 j
6 \3 s; j% H0 {7 u5 h0 j( T3 W) U
x = .6 + sqrt(0.1) * randn(5) & J0 Z8 ]6 P' [9 |9 n& B D& h" A% qx = 5 f2 z; a" }( p1 J0 L# i, t0.8713 0.4735 0.8114 0.0927 0.7672 q# t) M* c! U! |
0.9966 0.8182 0.9766 0.6814 0.6694+ X$ A! Z3 n! d9 @
0.0960 0.8579 0.2197 0.2659 0.30855 j5 I0 @; K, }* z7 n& G9 R
0.1443 0.8251 0.5937 1.0475 -0.0864- d: `( I+ t! H/ s( N- q
0.7806 1.0080 0.5504 0.3454 0.5813) G3 j* J" |* A7 n# }: |
其他类似函数：rand, randperm, sprand, sprandn $ ]3 y3 d/ `2 \) @, q, Y英文：2 i9 C% \ d5 k9 W
------------------------------------------------------------- 5 s' a8 L) H+ S% d- v. M8 z, Crandn 4 t( }1 ?; v- c7 ENormally distributed random numbers and arrays * _7 K5 P; x/ n; ]; w, n
. e* d% ~: N" E; g
Syntax9 D! {9 L8 l( a/ R9 C- o1 ^
Y = randn(n)! ]% I' u1 Q5 v; k" K
Y = randn(m,n)9 _. j% G3 F2 Z! @0 _" g
Y = randn([m n]): V" ?% F) V9 S9 k
Y = randn(m,n,p,...) ! X: {2 f( l2 O- Q! X! w+ Q, \* e, fY = randn([m n p...]) # o* q K( r: AY = randn(size(A)) 7 C+ Z; z' C) @, D2 Drandn 9 q+ |5 ^$ Y4 r, y3 Q% a2 E' Fs = randn('state')5 m2 b' c( X* G& R' W s
; ~, R0 F8 W) X, _$ N
Description4 }2 P6 k# E( u
The randn function generates arrays of random numbers whose elements are normally distributed with mean 0, variance σ^2 = 1 , and standard deviation σ = 1. * e0 `4 v3 A( i& N1 ^
; d# {' N$ Q7 x; B( Z
Y = randn(n) returns an n-by-n matrix of random entries. An error message appears if n is not a scalar. Y = randn(m,n) or Y = randn([m n]) returns an m-by-n matrix of random entries. Y = randn(m,n,p,...) or Y = randn([m n p...]) generates random arrays. Y = randn(size(A)) returns an array of random entries that is the same size as A. randn, by itself, returns a scalar whose value changes each time it's referenced. s = randn('state') returns a 2-element vector containing the current state of the normal generator. To change the state of the generator: randn('state',s)Resets the state to s. randn('state',0)Resets the generator to its initial state. randn('state',j)For integer j, resets the generator to its jth state. randn('state',sum(100*clock))Resets it to a different state each time.ExamplesExample 1. R = randn(3,4) may produce R = 4 y5 s3 i- G! r! L* ?; ?- \5 a! k1.1650 0.3516 0.0591 0.8717; ~5 H( A' b' T
0.6268 -0.6965 1.7971 -1.4462 + f9 S3 v! \. J' {0.0751 1.6961 0.2641 -0.7012 . M6 Z% p( ~4 [For a histogram of the randn distribution, see hist. Example 2. Generate a random distribution with a specific mean and variance . To do this, multiply the output of randn by the standard deviation , and then add the desired mean. For example, to generate a 5-by-5 array of random numbers with a mean of .6 that are distributed with a variance of 0.1 x = .6 + sqrt(0.1) * randn(5)8 q3 d ^( U5 u# _% V
x =. y8 }! m* x: [. e5 U" c# N
0.8713 0.4735 0.8114 0.0927 0.7672 9 k% R$ i+ T/ @& \0.9966 0.8182 0.9766 0.6814 0.6694 3 w3 j5 }' ?; }6 m' C2 J0.0960 0.8579 0.2197 0.2659 0.3085 2 M; J$ i0 x; u/ |- Q; j; T- [0.1443 0.8251 0.5937 1.0475 -0.0864 0 \9 l/ Z1 E4 T* D8 K; Y0.7806 1.0080 0.5504 0.3454 0.5813 9 }/ Z$ C5 g' v$ A* ]$ lSee Also rand, randperm, sprand, sprandn % ^4 r3 o+ ^9 Y" f2 Q : n6 Y3 D6 P2 m5 a- q' |. O二、Unbalanced or misused parentheses or brackets" }9 p+ D4 w) a