generate a sequence from matrix

Question

anshuman mishra 2019-7-29

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https://ww2.mathworks.cn/matlabcentral/answers/473951-generate-a-sequence-from-matrix

评论： dpb 2019-7-30

given matrix:

new =[
  28    21    14     7     0
  23    16     9     2     5
  18    11     4     3    10
  13     6     1     8    15
   8     1     6    13    20
   3     4    11    18    25
   2     9    16    23    30
   7    14    21    28    35]

i need to evaluate from 8th row,1st column.

i need to traverse from 0,2,3,1,1,3,2,0 (least element in each row)

and assign values 1 0 1 1 1 0 1 ( 1 when traversing diagonally and 0 when traversing sideways or upward but not backward or downward)

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Answer 1

dpb 2019-7-29

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https://ww2.mathworks.cn/matlabcentral/answers/473951-generate-a-sequence-from-matrix#answer_385297

在 MATLAB Online 中打开

Interesting...kinda' cute solution...altho note that the suggested answer is wrong; the minimum for row 7 is the 3 in column 2, not 4 in colum 3

[~,j]=min(flipud(new),[],2);
ix=diff(j)~=0;

Above returns

ix =
  7×1 logical array
   1
   0
   1
   1
   1
   0
   1
>> 

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anshuman mishra 2019-7-30

okay,thanks. i have a new issue:

given matrix

a=

16 8 0

13 5 3

10 2 6

7 1 9

4 4 12

1 7 15

2 10 18

5 13 21

when im traversing from 1 to 4 ( as underlined) it should go from 1 to 4 diagonally not vertically(The row above 1 has two 4's, so to avoid conflict i want to move diagonally instead of vertically).The previous code like it assigns 1 for diagonal movement should also work here,because since it goes vertically it gives me 0, whereas i want it to go diagonally,and get 1.

dpb 2019-7-30

Well, you've just broken any chance for a one-liner I can see... :)

You'll have to do some preprocessing to eliminate the duplicated minima where they exist before calling the above algorithm or have to go back afterwards and check for duplicates and clean up the result if founc.

Or, just loop from the git-go and don't try to be fancy and find each next location one-at-a-time accounting for the duplicates as you go.

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