Comparing numerical values of a 5x2 cell

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Pat
Pat 2020-3-31
评论： Image Analyst 2020-3-31
Hello,
I am trying to compare all values in a 5x2 array that are below a certain threshold, and preserve the corresponding data in its particular row. For example, let's say I have a total of 5 cars but need to check which car goes a certain speed. I have a 5x2 matrix where the first column is a string and the second column are integers. I need to develop an algorithm that will return each of the cars that is below a a certain speed, say, below equal to or below 55 mph:
Red Car 50
Blue Car 45
Green Car 30
Black Car 60
Yellow Car 55
Therefore my output would need to be:
Red Car 50
Blue Car 45
Green Car 30
Yellow Car 55
I am guessing that the best way to do this will be with a few loops and an if statement to check the condition, but I am just not sure how to go about this as I am pretty new to MatLab. Any tips would be appreciated.
Thanks,
Patrick
  2 个评论
the cyclist
the cyclist 2020-3-31
编辑：the cyclist 2020-3-31
How are your car data stored? In a cell array? A table? Can you upload the data in a *.mat file, instead of just describing it?
Also, I don't understand how the 2x2 array you mention comes into play.
Pat
Pat 2020-3-31
Yes, I made a mistake. In this case it is a 5x2 cell. I am not sure how to get the cell into an array because it is a cell of cells, if that makes sense.
What I tried to do below is go through each row, looking at only the second element of the row in mph. Then I check if it is below 55. If the speed is above 55, I set that whole row to blank, thus removing it from the array. The problem is that I am getting an error that says "
Undefined function 'ge' for input arguments of type 'cell'.
for rows=1:5
if (carData{rows,2} <= 55)
carData{rows,2}=[]
end
end

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回答（2 个）

Image Analyst
Image Analyst 2020-3-31
This will do it:
ca = {
'Red Car', 50;
'Blue Car', 45;
'Green Car', 30;
'Black Car', 60;
'Yellow Car', 55}
speeds = vertcat(ca{:, 2}) % Extract column 2.
slowSpeeds = speeds < 55 % See who is below 55
output = ca(slowSpeeds, :) % Extract only those below 55.
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Pat
Pat 2020-3-31
I think what the problem is is that right now I have my "ca" variable as a cell of cells instead of as a matrix with strings and integers.
Image Analyst
Image Analyst 2020-3-31
Wow, how/why did it get so complicated??? Try to avoid that. Like Akira says, use a table - that's the current best approach.
Anyway, attach your actual cell array in a .mat file and I'll try to straighten it out or simplify it.

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Akira Agata
Akira Agata 2020-3-31
I would recommend storing your data as a table variable before processing, like:
% Data
ca = {
'Red Car', 50;
'Blue Car', 45;
'Green Car', 30;
'Black Car', 60;
'Yellow Car', 55};
% Arrange to table
T = table(ca(:,1),cell2mat(ca(:,2)),'VariableNames',{'CarType','Speed'});
% Extract the data where speed <= 55 mph
idx = T.Speed <= 55;
Tout = T(idx,:);
  1 个评论
Pat
Pat 2020-3-31
Thanks.
When I try this, it says, "Error using cell2mat (line 52)
Cannot support cell arrays containing cell arrays or objects."
I have "ca" stored as a cell of cells instead of defined as strings and numbers. The file I need to do this to has thousands of cards, so I can't set every row manually...

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