how to use multiple 'for loop' for one function?

Question

Sierra 2022-6-24

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1747415-how-to-use-multiple-for-loop-for-one-function

评论： Kenneth Joseph Paul 2022-6-24

intersection_point = [];
for i = 1:length(mean_trajectory_double)-1
      for j = 1:length(RKSI_Arr_33R)
        for k = 1:length(RKSI_Arr_33R.Latitude)
        [I,check]=plane_line_intersect([mean_trajectory_double(i+1,1) mean_trajectory_double(i+1,2) NormalVectorsmean_trajectory_double(i+1,3)]...
            ,[mean_trajectory_double(i+1,1) mean_trajectory_double(i+1,2) mean_trajectory_double(i+1,3)]...
            ,[RKSI_Arr_33R(j).Longitude(k) RKSI_Arr_33R(j).Latitude(k)  RKSI_Arr_33R(j).BAlt(k)]...
            ,[RKSI_Arr_33R(j).Longitude(k+1) RKSI_Arr_33R(j).Latitude(k+1)  RKSI_Arr_33R(j).BAlt(k+1)]);
        intersection_point = [intersection_point;  ];
        end
      end
end
%% [I,check]=plane_line_intersect(n,V0,P0,P1)

I need to use multiple for loop for one function. I have used multiple for loop, but i have not used multiple for loop for one function.

this function need 4 input and 2 output(I,check). I is intersection_point and check is an indicator.

for more information about this function, https://kr.mathworks.com/matlabcentral/fileexchange/17751-straight-line-and-plane-intersection

What i want to do is that

when i is 1, j is 1 and k(1~100) is finished, it goes to i(1), j(2),k(1~100).

and j(1-200) is finisiehd, it goes to i(2),j(1),k(1~100) and i(2),j(2),k(1~100) like this.

if you need more clarification to answer my question, just tell me

Thanks.

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Jan 2022-6-24

Kenneth means a "break point". Click in the bar on the left side in the editor. Then a red dot appears. Matlab stops at this point and you can check the varaibels used in this line.

The break command is something else.

Kenneth Joseph Paul 2022-6-24

You need to use a "break point". As you said a "break" teminates the loop. A "break point" is used to temporarily pause the execution of the code. You can follow the page linked below, if you are not familiar with "breakpoint"

https://www.mathworks.com/help/matlab/matlab_prog/set-breakpoints.html

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Answer 1

Jan 2022-6-24

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1747415-how-to-use-multiple-for-loop-for-one-function#answer_992550

编辑：Jan 2022-6-24

Please post the complete error message, if you mention an error. This message contains the information, in which line the problem occurs. I guess, it is here:

for i = 1:length(mean_trajectory_double)-1
      for j = 1:length(RKSI_Arr_33R)
          % RKSI_Arr_33R is a struct array
        for k = 1:length(RKSI_Arr_33R.Latitude)
            % Then RKSI_Arr_33R.Latitude is a list of arrays            

The innermost FOR loop should look like:

        for k = 1:length(RKSI_Arr_33R(j).Latitude)
        %                            ^^^        

What is the purpose of this line:

intersection_point = [intersection_point; ];

This concatenates the array intersection_point with nothing. Maybe you want:

intersection_point = [intersection_point; I];

The readability of your code would profit fromusing much simpler names for the variables.

R = RKSI_Arr_33R;
M = mean_trajectory_double;
N = NormalVectorsmean_trajectory_double;
Intersection = [];
for i = 1:numel(M)-1
   for j = 1:length(R)
      Lat  = R(j).Latitude;
      Long = R(j).Longitude;
      BAlt = R(j).BAlt;
      for k = 1:numel(Lat)
         [I,check] = plane_line_intersect([M(i+1, 1:2), N(i+1,3)], ...
              M(i+1, 1:3), ...
              [Long(k),   Lat(k),   BAlt(k)], ...
              [Long(k+1), Lat(k+1), BAlt(k+1)]);
         intersection_point = [intersection_point; I];
      end
   end
end

In clear code, typos are much more obvious. In addition accessing a field in a struct costs time, so the simplified code runs even faster.

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Sierra 2022-6-24

the error message is in Korean. so I wrote like that.

and where the function code shoul be located? between for i = 1:length and for j=1:length or for k=1:length and end ?

Thanks Jan.

Jan 2022-6-24

编辑：Jan 2022-6-24

"and where the function code shoul be located?" - what does this mean? I've mentioned, where I assume the error and how to fix it. Then I've posted a cleaned version of the complete code you have posted.

Concerning the original question: If the code does not containbugs, it is not problem to use nested loops inside one function.

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