Remove certain elements from a matrix

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NT
NT 2016-4-15
回答： Roger Stafford 2016-4-16
I have a text file Pressure which has a lot of rows and two columns and I want to remove the rows and columns where the columns are equal to zero, and display the old graph and new graph on the same plot and this is what i have so far, I don't know what to put in the if statement.
% Copy data from Pressure to OldData
OldData = load('Pressure.txt');
% Copy OldData to NewData
NewData = OldData;
% Remove points where there are zeros
for i = 1:length(OldData)
if(OldData(i,2) == 0)
end
end
% Plot both in same plot:
plot(OldData(:,1),OldData(:,2),'--b',NewData(:,1),NewData(:,2), 'r')
  1 个评论
Azzi Abdelmalek
Azzi Abdelmalek 2016-4-15
Make your Question clear. Avoid details that are not important to resolve your problem. You can post a short example with expected result

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回答（2 个）

James Tursa
James Tursa 2016-4-15
编辑：James Tursa 2016-4-15
Replace this:
% Remove points where there are zeros
for i = 1:length(OldData)
if(OldData(i,2) == 0)
end
end
with this:
% Remove points where there are zeros
x = OldData(:,2)==0; % Logical indexes where column 2 is 0
NewData(x,:) = []; % Remove the rows where column 2 is 0
Roger Stafford
Roger Stafford 2016-4-16
Or you just write:
NewData = OldData(OldData(:,2)==0,:);

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