how to delet multiple rows with single criteria in matlab

I have 900 by 4 mixed data. The first column contains letter of atom and the rest column is the XYZ coordinates of the atom. The arrangement of the atom looks like H1;H2;H3.......... this three rows repeat it self until the number of rows are 900.

    x  y  Z
H1  1  2  3
*H2  2  4  7*
H3  3  0  0
H1  1  1  1
*H2  0  0  0*
H3  4  6  7
.
.
.
.

 So how can  i  remove those three rows ( H1;H2;H3) if x of H2 >=3 else keep it.the data is a cell array.The main point is i only take as a criteria the value of x corresponds to H2. From 900 rows 300 of them are H2.For instance If the first H2(second row) satisfy the criteria i want to delet H1;H2;H3 and got the next H2.If it doesn't satisfy the criteria  i will keep the three rows and go to the next H2.

Answer 1

[Guillaume]

Step 1: reshape the cell array so each row is H1 x y z H2 x y z H3 x y z:

new_c = reshape(c', 12, [])';

Step 2: find out which of the row of the reshaped cell array has x of H2 (column 6) above your threshold

rowstodelete = cell2mat(new_c(:, 6)) > 3;

Step 3: delete these rows:

new_c(rowstodelete, :) = [];

Step 4: reshape back to original n*4 columns

new_c = reshape(new_c', 4, [])'

[alex solomon]

Thank you so much!! If it is not to much to ask , how can i count the number of H1,H2 and H3 and the Total Number=H1+H2+H3 and put as a row header in my data. Firs row total number, 2nd row H1, 3rd row H2 and 4th row H3.

Answer 2

[Image Analyst]

Assuming your data is in cell array "data"

x = data{:, 2}; % Extract column 2.
rowsToDelete = x >= 3;
filteredData = data(~rowsToDelete, :);

Answer 3

[James Tursa]

Are you trying to delete all three H1, H2, H3 rows if any of the x values in those rows are >= 3? If so, in your example it looks like all the rows will be deleted since the first set has H3 x = 3 and the 2nd set has H3 x = 4. Is this correct? And is your data in a cell array? If so, here is one way:

c = your cell array;
xlimit = 3; % or whatever
x = repmat(any(reshape(cell2mat(c(:,2)),3,[])>=xlimit),3,1);
c(x(:),:) = [];

[alex solomon]

Sorry there was a error in my first question. Here is the correct one. So how can i remove those three rows ( H1;H2;H3) if x of H2 >=3 else keep it.the data is a cell array.The main point is i only take as a criteria the value of x corresponds to H2. From 900 rows 300 of them are H2.For instance If the first H2(second row) satisfy the criteria i want to delet H1;H2;H3 and got the next H2.If it doesn't satisfy the criteria i will keep the three rows and go to the next H2.

[James Tursa]

So something like this?

c = your cell array;
xlimit = 3; % or whatever
x = repmat([c{2:3:end,2}]>=xlimit,3,1);
c(x(:),:) = [];