matlab-hw4

% HW4
%  hW4 info
%
%  3. Use of continue: Consider the following script:
%  x = [1 -2 3 -4 5 0 2];
%  total = 0;
%  for i = 1:length(x)  == 7
%   if x(i)<0, continue; end
%   total=total+x(i);
%  end
%
%   a. What is the purpose of the script? What is the final value of "total"?
%   b. Can you rewrite the script using the while-loop instead?
%
%
%
%  9. 給定一向量 A，請寫一段程式 useIf01.m，利用 if-then-else 指令來依元素值不同 而印出不同訊息。舉例而言，當 A=[-1, 1, 0, 2+i] 時，你的程式碼應印出：
%  ◦A(1) = -1 是negative number
%  ◦A(2) = 1 是正數
%  ◦A(3) = 0 是零
%  ◦A(4) = 2+i 是複數
%  用下列 A 來測試你的程式，並將結果印出來：A = randn(20,1)+(rand(20,1)>0.7)*sqrt(-1);
%
%  10. 重複上一題，程式碼名稱為 useSwitch01.m，但是必須使用 switch-case-otherwise 指令來完成。
%  ------
%  use function in 9,10 and no Chinese.
function hw4()
    disp('problem 3a')
    fprintf('purpose: sum of positive number\n')

    x = [1 -2 3 -4 5 0 2];
    total=0;
    p=0;
    while( p < numel(x) )
        p=p+1;
        if x(p)<0, continue; end
        total=total+x(p);

    end
    fprintf('\nproblem 3b\n')
    fprintf('total = %g\n',total);

    %-------------------------------------------------
    fprintf('\nproblem 9: This is useIf01.m\n')
    resultStr=useIf01( randn(20,1)+(rand(20,1)>0.7)*sqrt(-1) );
    disp(resultStr);
    %-------------------------------------------------
    fprintf('\nproblem 9: This is useIf02.m, another method\n')
    resultStr=useIf02( randn(20,1)+(rand(20,1)>0.7)*sqrt(-1) );
    disp(resultStr);
    %-------------------------------------------------
    fprintf('\nproblem 10: This is useSwitch01.m\n')
    resultStr=useSwitch01( randn(20,1)+(rand(20,1)>0.7)*sqrt(-1) );
    disp(resultStr);
end

function str=useIf01(a)
    tag=cell(size(a));
    tag( a>0 & imag(a)==0) = {'positive number'};
    tag( a==0  & imag(a)==0) = {'zero'};
    tag( a<0  & imag(a)==0) = {'negative number'};
    tag( imag(a)~=0 ) = {'complex numbers'};

    str=[];
    for n=1:numel(a)
        if strcmp(tag(n),'positive number')
            str=[str,sprintf('a(%d) = %g is a %s\n',n ,a(n) ,tag{n} ) ];
        elseif strcmp(tag(n),'zero')
            str=[str,sprintf('a(%d) = %g is a %s\n',n ,a(n) ,tag{n} ) ];
        elseif strcmp(tag(n),'negative number')
                str=[str,sprintf('a(%d) = %g is a %s\n',n ,a(n) ,tag{n} ) ];
        elseif strcmp(tag(n),'complex numbers')
                str=[str,sprintf('a(%d) = %s is a %s\n',n ,num2str(a(n)) ,tag{n} ) ];
        else
                str=[str,sprintf('a(%d) not a numbers\n',n ,a(n) ) ];
        end
    end
end

function str=useIf02(a)
    % other method
    str=[];
    for n=1:numel(a)
        if isreal(a(n))
            if a(n) > 0
                str=[str,sprintf('a(%d) = %g is a positive number\n',n ,a(n) ) ];
            elseif a(n) < 0
                str=[str,sprintf('a(%d) = %g is a negative number\n',n ,a(n) ) ];
            else
                str=[str,sprintf('a(%d) = %g is a zero\n',n ,a(n) ) ];
            end
        elseif isnumeric(a(n))
            str=[str,sprintf('a(%d) = %s is a complex numbers\n',n ,num2str(a(n)) ) ];
        else
            str=[str,sprintf('a(%d) is not a complex numbers\n',n ,a(n) ) ];
        end
    end
end

function str=useSwitch01(a)

    tag=cell(size(a));
    tag( a>0 & imag(a)==0) = {'positive number'};
    tag( a==0  & imag(a)==0) = {'zero'};
    tag( a<0  & imag(a)==0) = {'negative number'};
    tag( imag(a)~=0 ) = {'complex numbers'};

    str=[];
    for n=1:numel(a)
        switch tag{n}
            case 'positive number'
                str=[str,sprintf('a(%d) = %g is a %s\n',n ,a(n) ,tag{n} ) ];
            case 'zero'
                str=[str,sprintf('a(%d) = %g is a %s\n',n ,a(n) ,tag{n} ) ];
            case 'negative number'
                str=[str,sprintf('a(%d) = %g is a %s\n',n ,a(n) ,tag{n} ) ];
            case 'complex numbers'
                str=[str,sprintf('a(%d) = %s is a %s\n',n ,num2str(a(n)) ,tag{n} ) ];
            otherwise
                str=[str,sprintf('a(%d) is not a complex numbers\n',n ,a(n) ) ];
        end
    end
end