Matlab第三次打卡

Task03：数据类型

语法知识

1.奇数阶魔方矩阵

魔方矩阵的设计思路之一，是构造一个扩展的零矩阵A，随后用顺序矩阵v填入A的相应对角线，再用行、列叠加使矩阵A的中心n阶矩阵零元素填满。最后取出中心n阶方阵，即得魔方矩阵。

下面为奇数阶魔方矩阵的程序，文件名为odd_magic.

 %This is program for creat a matrix of odd order magic
 clear 
 n=input('please input a odd number \n');
  if mod(n,2)==0
      'input number must be odd.';
  end
  n1=2*n-1;m=(n-1)/2;
  A=zeros(n1);
  for i=1:n
      for j=1:n
          v(i,j)=(i-1)*n+j;
      end
  end
  for k=1:m+1
      B=zeros(1,n-2+2*k);
      B(k:(k+n-1))=v(k,:);
      A=A+diag(B,n+1-2*k);
  end
  for k=m+2:n
     B=zeros(1,3*n-2*k);
     B(n-k+1:2*n-k)=v(k,:);
     A=A+diag(B,n+1-2*k);
  end
  if m==1
      A(4,:)=A(4,:)+A(1,:);
      A(2,:)=A(2,:)+A(5,:);
      A(:,4)=A(:,4)+A(:,1);
      A(:,2)=A(:,2)+A(:,5);
  else
      Bu=A(1:m,:);
      Bd=A((n1-m+1):n1,:);
      Bl=A(:,1:m);
      Br=A(:,(n1-m+1):n1);
      A(m+1:2*m,:)=A(m+1:2*m,:)+ Bd;
      A((n1-2*m+1):n1-m,:)=A((n1-2*m+1):n1-m,:)+Bu;
      A(:,m+1:2*m)=A(:,m+1:2*m)+Br;
      A(:,(n1-2*m+1):n1-m)=A(:,(n1-2*m+1):n1-m)+Bl;
  end
  M=A(m+1:(n1-m),m+1:(n1-m));     %取*n阶方阵，即为魔方矩阵

2.数据类型概述

3.字符型数组

实例演练

>> odd_magic
please input a odd number 
3
>> n

n =

     3

>> M

M =

     4     9     2
     3     5     7
     8     1     6

>> odd_magic
please input a odd number 
5
>> n

n =

     5

>> M

M =

    11    24     7    20     3
     4    12    25     8    16
    17     5    13    21     9
    10    18     1    14    22
    23     6    19     2    15

>> v

v =

     1     2     3     4     5
     6     7     8     9    10
    11    12    13    14    15
    16    17    18    19    20
    21    22    23    24    25

>> A

A =

     0     0     0     0     1     0     0     0     0
     0     0     0     6     0     2     0     0     0
     0     0    11    24     7    20     3     0     0
     0    16     4    12    25     8    16     4     0
    21     0    17     5    13    21     9     0     5
     0    22    10    18     1    14    22    10     0
     0     0    23     6    19     2    15     0     0
     0     0     0    24     0    20     0     0     0
     0     0     0     0    25     0     0     0     0

>> magic(5)

ans =

    17    24     1     8    15
    23     5     7    14    16
     4     6    13    20    22
    10    12    19    21     3
    11    18    25     2     9

>> sum(M)            %列元素之和的向量

ans =

    65    65    65    65    65

>> sum(M')             %行元素之和的向量

ans =

    65    65    65    65    65

>> trace(M)              %主对角线元素之和

ans =

    65

>> trace(M')               %反向主对角线元素之和

ans =

    65

【例3-19】建立字符串数组A='Today is Saturday.'及B='I want to eat ice-cream.'检查它们的长度，将他们进行水平连接和垂直连接。

>>  A =

    'Today is Saturday.'

>>  b='I want eat ice-cream.'

b =

    'I want eat ice-cream.'

>>  na=size(A)

na =

     1    18

>> nb=size(b)

nb =

     1    21

>> NA=strcat(A,b)

NA =

    'Today is Saturday.I want eat ice-cream.'

>> NB=strvcat(A,b)

NB =

    'Today is Saturday.   '
    'I want eat ice-cream.'

>> size(NB)

ans =

     2    21
>> double(NB)

ans =

    84   111   100    97   121    32   105   115    32    83    97   116   117   114   100    97   121    46    32    32    32
    73    32   119    97   110   116    32   101    97   116    32   105    99   101    45    99   114   101    97   109    46

>> k=findstr(s,'the')

k =

     6    30

或

>> k1=findstr('the',s)

k1 =

     6    30

>> S1='The area is at least 400 square meters';
>> newarea=strrep(S1,'400','1000')

newarea =

    'The area is at least 1000 square meters'

>> asii=char(reshape(32:127,32,3)')

asii =

  3×32 char 数组

    ' !"#$%&'()*+,-./0123456789:;<=>?'
    '@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_'
    '`abcdefghijklmnopqrstuvwxyz{|}~'

总结思考

1.在魔方矩阵程序运行方面存在一些问题，经过纠正最终得到正确结果，但具体的矩阵不是很清楚；掌握了一些求和的函数；

2.数据类型上对于字符串相关的函数有了理解和掌握。