How to extract entire rows based on values placed in a single column in a matrix?

Hi everyone,

I have a 100x10 table, let's call it CH_channel. i have got 3 questions. If you are able to find a solution for every task, you will be a hero to me, otherwise, if you manage to solve only the first task, it would be really appreciated as well.

1. in this matrix, i want to find all the values exceeding a value x (let's say 7) only in column number 5. Then I would like to retain all the values in the same row;
2. once done this, I would like to "crop" 1 row before the x value and 2 rows after it within the CH_channel.
3. I would like to create a new table in 3 dimension, where every "cropped" epoch represent a dimension (they are supposed to be trials).

note that if you end up with 2 consecutive rows where you have 2 or more values >7, you will need to start computing the rows to retain only from the first values exceding the x.

right now, I am stucked, please help.

the final results, according to the following table should be:

1. for the first point, the code should retain all the values in rows 8 and 12 (for all columns);
2. crop/cut all the values within rows 7:10 and from rows 11:14
3. with the values "extracted" outr of the matrix CH_channel, i would like to create a brand new 3D matrix, where these "cropped" rows represent different epochs (or trials)

CH_channel = array2table(randi(8,16, 5))

CH_channel = 16×5 table
    Var1    Var2    Var3    Var4    Var5
    ____    ____    ____    ____    ____

     3       8       2       5       2  
     1       3       3       4       7  
     6       1       4       1       3  
     4       4       8       3       6  
     5       4       2       5       5  
     5       3       2       5       4  
     4       1       1       6       6  
     8       6       1       2       8  
     7       7       1       2       3  
     5       2       1       2       2  
     4       2       6       5       6  
     7       6       5       4       8  
     7       7       2       6       7  
     5       7       1       3       2  
     3       4       8       4       2  
     6       2       3       6       3  

[James Tursa]

What have you done so far? What specific problems are you having with your code? What would be the desired output for the example table you generated above?

[David Hill]

If your data is all numbers, why not store the data in a cell array (some of your matrices will be different sizes). Generate your tables on the back end when necessary.

[enzo]

@James Tursa my progress toward my final goal are pathetic. I won't share my attempt as they are useless. I tried a bunch of things, but non of them seems to work properly. Specific problems: i couldn't even find a proper solution for point 1 in orer to spot the proper values. Function Y= find(x); and function idx = any(Table{:,:}>4,2); did not worked out. for the final result, I have update the question. Check the bottom lines. thanks so much for your efforts

[Voss]

1. in this matrix, i want to find all the values exceeding a value x (let's say 4) only in column number 33. Then I would like to retain all the values in the same row;

% make the table:
CH_channel = array2table(randi(10,100, 33))

CH_channel = 100×33 table
    Var1    Var2    Var3    Var4    Var5    Var6    Var7    Var8    Var9    Var10    Var11    Var12    Var13    Var14    Var15    Var16    Var17    Var18    Var19    Var20    Var21    Var22    Var23    Var24    Var25    Var26    Var27    Var28    Var29    Var30    Var31    Var32    Var33
    ____    ____    ____    ____    ____    ____    ____    ____    ____    _____    _____    _____    _____    _____    _____    _____    _____    _____    _____    _____    _____    _____    _____    _____    _____    _____    _____    _____    _____    _____    _____    _____    _____

      5      1       10      1       4        2      3       4        6       2        3        3        3        5       10        9        1        4        7        6        3        6        3        8       10        8        9        7        2        4        2        9        4  
      5      4        5      1       6        8      6       2        3       1        3        1        8        7        2        5        2        5        8        2       10        3        2        9        4        1        1        6       10        6        4        6        8  
      9      4        3      8       6        6      3       2        1       6       10        4        5        1        3        5        1       10       10        7        4        4        8        1        4        8        7        9        9        6        4        3        6  
      8      3        2      9       5        3      8       3        9      10        7        6        7        6        8        4        5        6        3        8        8       10        5        4        9       10        6        8        8        8        1        7        8  
     10      1        3      5       7        6      9       1        5       7        5        1       10        8        1        8        8        6        7        2        3        3       10       10        9        9        2        2        5        8        6        9        4  
     10      8        6      8       5        5      3       3        6       6       10        8       10        8       10        4        3        9        6        9        5       10        1        2        3        4        8        1        1        4        8        9        5  
     10      9        2      8       7       10      6       3       10       4       10        5        4        4        1        5       10       10        8        8        6        8        6        8        1       10        3        6        2        9        3        9       10  
      4      8        1      2       4        5      8       2        3       8        2        5        5       10        1        3        9        9       10        9        2        2        5        6       10        6        4        5        2        3        4        6        8  
      5      8        7      3       2        1      3       5        1       7        8        5        2        4        8        6        2        6        4       10        5        3        7        6        5        9        1        2        6        8        1        1        5  
      4      1        8      5       7        7      1       4       10       4        1        7       10        9        6        2        4        1        3        8        1        6        9        5        6        8        4        4        9        8        6        8        6  
      5      3        5      8       2        6      9       9        9       2        2        6        4        6        1        3        6       10        5        1        4        1        7        3        4        8        9        8        2        8        4        1        8  
     10      7        8      5       9        4      4       5        1       6        7        7        1       10        9        8        6        1        7       10        9        8        3        9        9        4        3        4        9        8       10        4        9  
     10      2       10      9       3        4      5       5        8       6        4        1        6        4        3        9        4        8        9        6        4        5        9        7        7        9       10        2        6        1        4        7        9  
      6      9        4      1       3        6      5       7        6       5        1        7        5        2        9       10        8        1        6        2        2        6        3        3        4       10        6        8        4        6        8        8        2  
      6      1        6      2       4        6      7       8        2       8        6        9        9        3        4        2        5        6       10        2        6        6        3        7        9        2        3        3        9        3        9        7        7  
      2      7        8      2       5       10      7       3        4       6        1        2        2        8        1        8        2        9       10        1        4        1       10        3        2       10        8        6        3       10        5        5        8  

% rows where column 33 > 4:
idx = CH_channel{:,33} > 4

idx = 100×1 logical array
   0
   1
   1
   1
   0
   1
   1
   1
   1
   1
   1
   1
   1
   0
   1
   1
   0
   1
   0
   1
   1
   0
   1
   0
   1
   1
   0
   0
   0
   0
   1
   0
   1
   0
   0
   1
   1
   0
   0
   1
   0
   1
   0
   1
   0
   0
   1
   1
   1
   1
   1
   1
   1
   1
   1
   0
   0
   1
   0
   1
   1
   1
   1
   1
   1
   0
   0
   1
   1
   0
   1
   1
   0
   1
   1
   0
   1
   1
   1
   1
   0
   1
   1
   1
   0
   0
   0
   0
   0
   1
   1
   1
   0
   0
   1
   0
   1
   1
   0
   1

% keep those rows:
values_to_keep = CH_channel(idx,:)

values_to_keep = 62×33 table
    Var1    Var2    Var3    Var4    Var5    Var6    Var7    Var8    Var9    Var10    Var11    Var12    Var13    Var14    Var15    Var16    Var17    Var18    Var19    Var20    Var21    Var22    Var23    Var24    Var25    Var26    Var27    Var28    Var29    Var30    Var31    Var32    Var33
    ____    ____    ____    ____    ____    ____    ____    ____    ____    _____    _____    _____    _____    _____    _____    _____    _____    _____    _____    _____    _____    _____    _____    _____    _____    _____    _____    _____    _____    _____    _____    _____    _____

      5       4       5      1       6        8      6        2       3       1        3        1        8        7        2        5        2        5        8        2       10        3        2        9        4        1        1        6       10        6        4        6        8  
      9       4       3      8       6        6      3        2       1       6       10        4        5        1        3        5        1       10       10        7        4        4        8        1        4        8        7        9        9        6        4        3        6  
      8       3       2      9       5        3      8        3       9      10        7        6        7        6        8        4        5        6        3        8        8       10        5        4        9       10        6        8        8        8        1        7        8  
     10       8       6      8       5        5      3        3       6       6       10        8       10        8       10        4        3        9        6        9        5       10        1        2        3        4        8        1        1        4        8        9        5  
     10       9       2      8       7       10      6        3      10       4       10        5        4        4        1        5       10       10        8        8        6        8        6        8        1       10        3        6        2        9        3        9       10  
      4       8       1      2       4        5      8        2       3       8        2        5        5       10        1        3        9        9       10        9        2        2        5        6       10        6        4        5        2        3        4        6        8  
      5       8       7      3       2        1      3        5       1       7        8        5        2        4        8        6        2        6        4       10        5        3        7        6        5        9        1        2        6        8        1        1        5  
      4       1       8      5       7        7      1        4      10       4        1        7       10        9        6        2        4        1        3        8        1        6        9        5        6        8        4        4        9        8        6        8        6  
      5       3       5      8       2        6      9        9       9       2        2        6        4        6        1        3        6       10        5        1        4        1        7        3        4        8        9        8        2        8        4        1        8  
     10       7       8      5       9        4      4        5       1       6        7        7        1       10        9        8        6        1        7       10        9        8        3        9        9        4        3        4        9        8       10        4        9  
     10       2      10      9       3        4      5        5       8       6        4        1        6        4        3        9        4        8        9        6        4        5        9        7        7        9       10        2        6        1        4        7        9  
      6       1       6      2       4        6      7        8       2       8        6        9        9        3        4        2        5        6       10        2        6        6        3        7        9        2        3        3        9        3        9        7        7  
      2       7       8      2       5       10      7        3       4       6        1        2        2        8        1        8        2        9       10        1        4        1       10        3        2       10        8        6        3       10        5        5        8  
      2       5       3      6       7        3      9        8       2       4        2        2       10        4        8        9        5        3       10        8        8       10        2        5        4        3       10        3        9        2        4        1        6  
      4      10       3      3       5        7      9        6       6      10        2        9        5        2        7        7        9        3        1        8        7        6        7       10       10        3        2        2        1        2        4       10        7  
     10       5       9      3       2        6      5       10       9       3        5        5        7        9        2        8        8        5        3        9        7        3        2        8        7        1        6        5        2        4       10        7       10  

[enzo]

this seems like a beatiful and smooth solution for my first step tpward my final goal. thansk a lot. I will work it out and try to reach the next steps

Answer 1

[David Hill]

H = array2table(randi(10,100, 33));
f=find(H{:,33}>4);
f=f(diff(f)>1);%removes consecutive rows >4
for k=1:length(f)
    c{k}=H(max(1,f(k)-5):min(100,f(k)+10),:);
end
c

c = 1×28 cell array
    {11×33 table}    {13×33 table}    {16×33 table}    {16×33 table}    {16×33 table}    {16×33 table}    {16×33 table}    {16×33 table}    {16×33 table}    {16×33 table}    {16×33 table}    {16×33 table}    {16×33 table}    {16×33 table}    {16×33 table}    {16×33 table}    {16×33 table}    {16×33 table}    {16×33 table}    {16×33 table}    {16×33 table}    {16×33 table}    {16×33 table}    {16×33 table}    {16×33 table}    {16×33 table}    {16×33 table}    {15×33 table}