MatLab HW1 CH4-6

 MatLab HW1 CH4-6 

-- 40843245 

preface

this is my ans of HW in numerical analysis.

I don't put my question in this article. I just put my answer.

Question in the reference book in the following link.

info

HW1

CH4-6

HW Date:2021/10/22-2021/10/29

Reference Book

博客來-MATLAB程式設計實務(第五版)(附範例光碟) (books.com.tw)

CH4-6  

[Code] 

%MatLab HW CH4-6 

%HW Date:2021/10/22 

  

%clear workspace 

clear 

%clear command window 

clc 

  

%create a symbolic variable 

x=sym ('x'); 

C(x)=0.1*x^2+7*x+210; 

vec1=[1:2:30]; 

%ans 

y=C(vec1) 

 

[Ans] 

y= 

[2171/10, 2319/10, 495/2, 2639/10, 2811/10, 2991/10, 3179/10, 675/2, 3579/10, 3791/10, 4011/10, 4239/10, 895/2, 4719/10, 4971/10] 

 

CH4-26 

[Code] 

%MatLab HW CH4-26 

%HW Date:2021/10/22 

  

%clear workspace 

clear 

%clear command window 

clc 

  

%input data 

strdata=["1","Computer","English","Chinese","Math"; 

      "1","93","89","90","82"; 

      "2","90","95","88","87"; 

      "3","78","84","81","82"; 

      "4","89","89","90","82"; 

      "5","93","92","90","88"; 

      "6","89","90","88","78"; 

      "7","85","87","83","83"]; 

%convert string matrix to cell matrix 

celldata=cellstr(strdata) 

[strdata_numRow,strdata_numCol]=size(strdata); 

%numRow mean how many student are there? 

%I have to subtract 1 since first row of strdata is subject. 

numRow=strdata_numRow-1; 

%create table of student scores. 

  

  

intdata=strdata(2:numRow,:) 

  

%{ 

function [total,avg]=totalCell(A,startRow,endRows,startCols,endCols) 

for idx=startRow:endRows 

        total(idx)=sum(A(idx)) 

        avg(idx)=total(idx)/(endRow-startRow) 

    end 

end 

  

cellfun(@a totalCell(a,2,numRow,2,6),intdata) 

%} 

 

[Ans] 

celldata = 

  

  8×5 cell array 

  

    {'1'}    {'Computer'}    {'English'}    {'Chinese'}    {'Math'} 

    {'1'}    {'93'      }    {'89'     }    {'90'     }    {'82'  } 

    {'2'}    {'90'      }    {'95'     }    {'88'     }    {'87'  } 

    {'3'}    {'78'      }    {'84'     }    {'81'     }    {'82'  } 

    {'4'}    {'89'      }    {'89'     }    {'90'     }    {'82'  } 

    {'5'}    {'93'      }    {'92'     }    {'90'     }    {'88'  } 

    {'6'}    {'89'      }    {'90'     }    {'88'     }    {'78'  } 

    {'7'}    {'85'      }    {'87'     }    {'83'     }    {'83'  } 

 

CH5-8 

[Code] 

%MatLab HW CH5-8 

%HW Date:2021/10/22 

  

%clear workspace 

clear 

%clear command window 

clc 

  

%create a symbolic variable 

t=sym ('t'); 

F(t)=1200/(1+28*exp(-0.2*t)); 

  

%(a)ans 

result1=F(10) 

%(b)ans 

vec1=10:5:50 

result2=F(vec1) 

 

[Ans] 

[1200/(28*exp(-2) + 1), 1200/(28*exp(-3) + 1), 1200/(28*exp(-4) + 1), 1200/(28*exp(-5) + 1), 1200/(28*exp(-6) + 1), 1200/(28*exp(-7) + 1), 1200/(28*exp(-8) + 1), 1200/(28*exp(-9) + 1), 1200/(28*exp(-10) + 1)] 

 

CH5-17 

[Code] 

%MatLab HW CH5-17 

%HW Date:2021/10/22 

  

%clear workspace 

clear 

%clear command window 

clc 

  

%way1: 

%solve it 

syms x y z; 

equ1=3*x-3*y+z==2 

equ2=x-y+z==1 

equ3=7*x+5*y-z==-5 

  

%find a solution of equation 

sol=solve([equ1,equ2,equ3],[x,y,z]) 

%ans 

x=sol.x 

y=sol.y 

z=sol.z 

 

[Ans] 

sol =  

  

  struct with fields: 

  

    x: -1/6 

    y: -2/3 

    z: 1/2 

  

  

x = 

  

-1/6 

  

  

y = 

  

-2/3 

  

  

z = 

  

½ 

 

[Screenshot] 

 

 

CH6-11 

[Code] 

%MatLab HW CH6-11 

%HW Date:2021/10/22 

  

%clear workspace 

clear 

%clear command window 

clc 

  

%way1 

%original way - for loop 

result=1 

n=1001 

for idx=1:n:1 

    result=result*((-1)^idx) 

end 

result 

  

%way2 

%simplified math formula 

%since //(-1)^2=1,(-1)^3=(-1),... 

%ans=1 when n is even, ans=-1 when n is odd. 

  

n=1001 

%ans 

result=mod(n,2)*2-1 

 

[Ans] 

result = 

  

     1 

 

心得 
從寫作業中學到許多東西，其中也包括老師上課沒教到的東西了。 

如:CH5-17 

我學到了如何用程式解方程式。 

我google了一 下發現matlab很強大，只要一行就可得到答案。 

(先寫好方程式，透過solve函式得到結構解)