Setting X as a column of a matrix

2012 9 11
3 个回答
回答已采纳
4 次查看（30 天）

0 个投票

So I have another question: How do i tell MATLAB to go thru the matrix and take the second column of this and apply it to the if statement i have coded below:
M = [1, 80.8 %A Matrix for the grades
2, 79
3, 87.4
4, 74.2
5, 82
6, 85]
%The following if, else if and else statement calculates the grades based
%on the values of X.
if X<60
y = F
elseif X>=60 & X<70
y = D
elseif X>=70 & X<80
y = C
elseif X>=80 & X<90
y = B
else
y = A
end
After I do that, I want it to output into a matrix like the one above, but with another column where the y will go.

请先登录，再回答此问题。

 采纳的回答

Matt Fig
Matt Fig 2012-9-11
编辑：Matt Fig 2012-9-11

0 个投票

Use a FOR loop to loop over the rows of column 2. But you are going to want to define A,B,C,D,F or you will get errors. Unless you mean 'A','B','C','D','F'. And to store the values, assign each one to a position in an array.
for ii = 1:length(M)
X = M(ii,2); % Assign this value to X, each time through
if X<60
y = F;
elseif X>=60 & X<70
y = D;
elseif X>=70 & X<80
y = C;
elseif X>=80 & X<90
y = B;
else
y = A;
end
GR(ii) = y
end

3 个评论
显示 1更早的评论 隐藏 1更早的评论

Jonathon
Jonathon 2012-9-13
Well what I am looking for, to be more specific, is for it to take the values of column 2, assign a letter grade, and be able to print the resulting values into a new matrix.
Matt Fig
Matt Fig 2012-9-13
编辑：Matt Fig 2012-9-13
So did you try it? Like I said, you should use 'A' instead of A, 'B' instead of B...
M = [1, 80.8 %A Matrix for the grades
2, 79
3, 87.4
4, 74.2
5, 82
6, 85]
for ii = 1:length(M)
X = M(ii,2);
if X<60
y = 'F';
elseif X>=60 & X<70
y = 'D';
elseif X>=70 & X<80
y = 'C';
elseif X>=80 & X<90
y = 'B';
else
y = 'A';
end
GR(ii) = y;
end
GR.'
Jonathon
Jonathon 2012-9-13
Yeah I have, thanks I've gathered all I need.

请先登录，再进行评论。

更多回答（2 个）

Matt Kindig
Matt Kindig 2012-9-11

0 个投票

You can also do this using logical indexing, which is a more "Matlab-y" way to do this problem...
y = repmat('A', size(M(:,1))); %set default grade to 'A'
X = M(:,2);
%these various truth conditions assign letter grade appropriately
y(X<60) = 'F';
y(X>=60 & X<70) = 'D';
y(X>=70 & X<80) = 'C';
y(X>=80 & X<90)= 'B';
Andrei Bobrov
Andrei Bobrov 2012-9-12
编辑：Andrei Bobrov 2012-9-13

0 个投票

M = [1, 80.8 %A Matrix for the grades
2, 79
3, 87.4
4, 74.2
5, 82
6, 85];
x = cellstr(['F';('D':-1:'A')']); % OR x = ['F';('D':-1:'A')'];
[a,b] = histc(M(:,2),[-inf,(6:9)*10,inf]);
out = x(b);
OR
x = ['F';('D':-1:'A')'];
out = x(sum(bsxfun(@gt,M(:,2),[-inf,(6:9)*10,inf]),2));

类别

在 帮助中心 和 File Exchange 中查找有关 Logical 的更多信息

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by