For Loop Question on index

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Michael Angeles
Michael Angeles 2022-1-18
评论： Michael Angeles 2022-1-18
I have an example data:
Column 1 is Student Number, Column 2-4 are grades
1.0 68.0 45.0 92.0
2.0 83.0 54.0 93.0
3.0 61.0 67.0 91.0
4.0 70.0 66.0 92.0
5.0 75.0 68.0 96.0
6.0 82.0 67.0 90.0
How can I create a for loop that would sum Column 2-4 and relate it back to the student number.
It should print out: "Student" 1 "Total_score" 205 (This added columns 2-4)"
Thanks!
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James Tursa
James Tursa 2022-1-18
编辑：James Tursa 2022-1-18
What have you done so far? What specific problems are you having with your code? Are you required to use a for-loop?

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采纳的回答

Voss
Voss 2022-1-18
Ran in:
data = [ ...
1.0 68.0 45.0 92.0; ...
2.0 83.0 54.0 93.0; ...
3.0 61.0 67.0 91.0; ...
4.0 70.0 66.0 92.0; ...
5.0 75.0 68.0 96.0; ...
6.0 82.0 67.0 90.0; ...
];
total = sum(data(:,2:4),2);
for i = 1:size(data,1)
fprintf('"Student" %d "Total_score" %g (This added columns 2-4)"\n',data(i,1),total(i,1));
end
"Student" 1 "Total_score" 205 (This added columns 2-4)" "Student" 2 "Total_score" 230 (This added columns 2-4)" "Student" 3 "Total_score" 219 (This added columns 2-4)" "Student" 4 "Total_score" 228 (This added columns 2-4)" "Student" 5 "Total_score" 239 (This added columns 2-4)" "Student" 6 "Total_score" 239 (This added columns 2-4)"
Or, if you really want to do the sum in a loop:
total = NaN(size(data,1),1);
for i = 1:size(data,1)
total(i) = data(i,2)+data(i,3)+data(i,4);
end
for i = 1:size(data,1)
fprintf('"Student" %d "Total_score" %g (This added columns 2-4)"\n',data(i,1),total(i,1));
end
"Student" 1 "Total_score" 205 (This added columns 2-4)" "Student" 2 "Total_score" 230 (This added columns 2-4)" "Student" 3 "Total_score" 219 (This added columns 2-4)" "Student" 4 "Total_score" 228 (This added columns 2-4)" "Student" 5 "Total_score" 239 (This added columns 2-4)" "Student" 6 "Total_score" 239 (This added columns 2-4)"
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Voss
Voss 2022-1-18
The second 2 is to tell the sum() function to sum along the 2nd dimension. See the description in the documentation here.

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