Drop all entries of a category based on one condition

I'm working with a 745820x4 table containing the PermNo., date, CUSIP and stock price of a multitude of shares. The data is sorted such that the full time series of a stock is listed below the full time series of the following stock and so forth. (Pls see photo below). I am trying to exclude companies from the sample once their share price drops below 1USD based on the unique identifier CUSIP in column 3. I have started to try with a combination of a for and an if loop but i cant figure out how it could even work. So for example in the picture below, the share price of the company with the CUSIP 89026070 has share price below USD 1 and i now want to drop all entries for the respective comany.

nRows = size(crsp,1)
for i = 1:nRows
    if crsp{i,4}<1 
...
    end

Answer 1

[Cris LaPierre]

nRows = height(crsp)
for i = 1:nRows
    if crsp.PRC(i)<1 
        crsp(crsp.CUSIP==crsp.CUSIP(i),:)=[];
    end
end

It might also be possible to use logical indexing and ismember to accomplish this without using a for loop.

[Simon Jurgies]

Thank you Sir! Your first solution worked as I am looking for the price to fall below USD1 not the CUSIP. I appreciate your help!