Question

我有一个if-else if构造，根据0-100的标记给我A，B，C，D，F等级。

if (mark > 100) | (mark < 0)
disp('Invalid mark');
return; % Exit from the program.
end % Of first if statement
if mark >= 80 % Mark is in range 80 - 100.
grade = 'A';
elseif mark >= 70 % Mark is in range 70 - 79.
grade = 'B'; 
elseif mark >= 60 % Mark is in range 60 - 69.
grade = 'C';
elseif mark >= 50 % Mark is in range 50 - 59.
grade = 'D'  
else % Mark is in range 0 - 44.
grade = 'F';
end
disp(grade);

现在，我有另一个长度为Ax1的数字标记向量（从0到100），称为＆＃39;标记＆＃39;。我不确定;如何通过这行代码输入每个数字标记，以实现成绩的输出向量？

Answer 1

您可以按照矢量化方式执行此操作：

save('your_filename.mat', 'database')

在该示例中，这给出了char矢量od等级

grade_names = 'FDCBA';
th = [50 60 70 80]; % thresholds that define the grades
marks = [75 70 33 99 88 58]; % data
grades_num = 1 + sum(bsxfun(@ge, marks(:).', th(:) ), 1); % vector with numbers
    %  indicating grade: 1 for the first ('F'), 2 for the second ('D') etc
grades = grade_names(grades_num);

如果您更喜欢单元格数组输出，请将第一行更改为

grades =
BBFAAD

将给出

grade_names = {'F' 'D' 'C' 'B' 'A'};

Answer 2

试试这个：

for i=1:length(marks) =标志标记（I）;`

后面跟着你的代码并为for循环添加一个结尾。您也可以将等级放在矢量中，而不仅仅是显示它们。

Answer 3

这是另一个与Luis Mendo的答案略有不同的解决方案：

if numel(find((mark > 100) | (mark < 0))) > 0
    disp('Invalid mark');
    return; % Exit from the program.
end % Of first if statement
%array of break points
brkpnt = [0 50:10:80 101];
%distance between breakpoints
cnt = diff(brkpnt);
%table of grades corresponding to related marks
Grades = repelem('FDCBA', cnt);
%the result. 1  added to mark to make indices greater than 0
grade = Grades(mark + 1)

或者您可以使用简单的矢量化形式

grade(mark >= 80) = 'A';
grade(mark < 80 & mark >= 70) = 'B';
grade(mark < 70 & mark >= 60) = 'C';
grade(mark < 60 & mark >= 50) = 'D';
grade(mark < 50) = 'F';

我将这些方法与结果的基准比较：

-----------repelem method---
Elapsed time is 0.00621986 seconds.
-----------bsxfun method---
Elapsed time is 0.022429 seconds.
-----------simple vectorized method---
Elapsed time is 0.0253041 seconds.
-----------for loop method---
Elapsed time is 7.7302 seconds.

基准：Online Demo

从if-else语句返回Grades向量

3 个答案: