Split array in 3 groups by using one column values

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Annick 2020-2-24

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https://ww2.mathworks.cn/matlabcentral/answers/507247-split-array-in-3-groups-by-using-one-column-values

编辑： Marta G 2020-2-25

采纳的回答： Marta G

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Hi,

I would like to split my data in 3 groups based on the values in axis 1

x = < 25 i would like to get a 0

x = > 25 < 419 i would like to get a 1

x = > 419 i would like to get a 2

how can I do this?

% Clear memory
clear; close all;
% Load data
T=readtable('SC01001 (2018-11-23)15sec.csv','PreserveVariableNames',true)
x1=T(:,1); %Date
x2=T(:,2); % Time
y1=T(:,3); % Axis 1
if 
    y1 <25 
    y1  = 0
elseif 
        y1 25>y1<419
        y1 = 1
elseif 
    y1 >419
    y1 = 2
 
end

采纳的回答

Marta G 2020-2-24

0
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/507247-split-array-in-3-groups-by-using-one-column-values#answer_417123

编辑：Marta G 2020-2-24

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You shouldnt use a vector in a if condition.

In your case, it would be more effective to use this

loc=find(y1<25);
y(loc)=0;
loc1=find(y1>25 & y1<419);
y(loc1)=1;
loc2=find(y1>419);
y(loc2)=2;

If you are new to matlab you might understand the problem better with a for loop.

for i=0:length(y1)
    if(y1(i)<25)
        y(i)=0;
    elseif (y1(i)>25 & y1(i)<419)
        y(i)=1;
    else
        y(i)=2;
    end
end

I prefer to not rewrite any variable i am using until it is completely necessary.

Make sure you really need those intervals and consider what you have to do if y1=25 since in your original code it would not enter any if else condition

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Annick 2020-2-25

Everything above the for loop works for me. This is the screen I get. Even when I try the xlsx file, i keep getting the same error message

Marta G 2020-2-25

编辑：Marta G 2020-2-25

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Hello,

Thank you Ankit for your correction

There is a step missing:

x1=T(:,1); %Date
x2=T(:,2); % Time
y1=table2array(T(:,3)); % Axis 1
for i=1:length(y1)
    if(y1(i)<25)
        y(i)=0;
    elseif (y1(i)>25 & y1(i)<419)
        y(i)=1;
    else
        y(i)=2;
    end
end

Make sure in future problems that you read the error and understand what it means, as that line missing is easily solvable. If you need matrix or vectors instead of table you can use table2array: https://es.mathworks.com/matlabcentral/answers/380821-how-to-convert-table-to-matrix

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