Delete data with some requirements

Question

Skydriver 2019-7-16

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/471940-delete-data-with-some-requirements

评论： Joel Handy 2019-7-16

采纳的回答： Star Strider

Xsample_data.txt

I have a coding like this:

Zx= zeros(size(X));

Zy=zeros(size(Y));

for i=1:length(X);

if Zx(i)<2.5 && Zx(i)>-2.5 && Zy(i)<2.5 && Zy(i)>-2.5

Zx(i) = (X(i) - Mean_X)/Std_X;

Zy(i) = (Y(i) - Mean_Y)/Std_Y;

else

Zx(i) && Zy(i) == 0

end

rowsToDelete = (Zx < -2.5 | Zx > 2.5) & (Zy <= -2.5 & Zy >= 2.5);

Xscore(rowsToDelete) = []; % Set to null.

Yscore(rowsToDelete) = []; % Set to null.

OutZscore=[X Y Zx Zy];

I also attach my data, two first coloumn is X and Y and two second column is Zx and Zy. X and Zx is a partner and Y and Zy is partner to in the same row.

I want to delete my X dan Y data with the requirement is X data wil be deleted is the requirement will explain such as (Zx<-2.5 and Zx>2.5) and (Zy<-2.5 and Zy>2.5).

The result is not satified.

I want to plot the data to compare the process before and after deleted.

Is there any one can help me I would be appreciate.

Thx

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Skydriver 2019-7-16

Thank you Joel Handy with your respond. I just put in the file of data input the out put of Zx and Zy. I want to show the result of my calculation so the row number 95th until the end wil be deleted. But I still don't know how to process for deleting. The requirement must be part of the data X and Y will be removed.

Joel Handy 2019-7-16

在 MATLAB Online 中打开

I think maybe you are looking for:

X = X(rowsToKeep);
Y = Y(rowsToKeep);
Zx = Zx(rowsToKeep);
Zy = Zy(rowsToKeep);

Or

X(~rowsToKeep) = [];
Y(~rowsToKeep) = [];
Zx(~rowsToKeep) = [];
Zy(~rowsToKeep) = [];

Not that in the latter example, you arent setting anything to null, you are setting them to "empty", i.e. deleting them.

Also as far as plotting, Star Striders answers should be what you are looking for.

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Answer 1

Star Strider 2019-7-16

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/471940-delete-data-with-some-requirements#answer_383426

在 MATLAB Online 中打开

Try this:

D = load('Xsample_data.txt');
X  = D(:,1);
Y  = D(:,2);
Zx = D(:,3);
Zy = D(:,4);
Lvx = (Zx < -2.5) & (Zx > 2.5);
Lvy = (Zy < -2.5) & (Zy > 2.5);
RowsToDelete = Lvx & Lvy;
figure
plot(X, Y)
hold on
plot(Zx, Zy)
hold off
grid
figure
plot(X(~RowsToDelete), Y(~RowsToDelete))
hold on
plot(Zx(~RowsToDelete), Zy(~RowsToDelete))
hold off
grid

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Star Strider 2019-7-16

在 MATLAB Online 中打开

Try this:

Lvx = (Zx < -2.5) | (Zx > 2.5);
Lvy = (Zy < -2.5) | (Zy > 2.5);
RowsToDelete = Lvx & Lvy;
figure
plot(X, Y, '-pb')
hold on
plot(X(~RowsToDelete), Y(~RowsToDelete), '-pr')
hold off
grid

Experiment with the plot to get the result you want.

Star Strider 2019-7-16

在 MATLAB Online 中打开

‘How about the value of Zx and Zy is above 3 maybe in other case. It should be also deleted.’

Set the upper limit to 3:

Lvx = (Zx < -2.5) | (Zx > 2.5);
Lvy = (Zy < -2.5) | (Zy > 2.5);

That will change the upper limit, so that only values >3 (and <-2.5) will be deleted. All values >3 will already be deleted with the current threshold of >2.5.

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Answer 2

Skydriver 2019-7-16

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/471940-delete-data-with-some-requirements#answer_383432

Dear Star Rider and Joel Handy.

I tried to combine your suggestion and the coding is like this:

D = load('Xsample_data.txt');

X = D(:,1);

Y = D(:,2);

Zx = D(:,3);

Zy = D(:,4);

Mean_X = mean(X)

Std_X = std(X)

Mean_Y = mean(Y)

Std_Y = std(Y)

Zx= zeros(size(X));

Zy=zeros(size(Y));

for i=1:length(X);

if Zx(i)<2.5 && Zx(i)>-2.5 && Zy(i)<2.5 && Zy(i)>-2.5

Zx(i) = (X(i) - Mean_X)/Std_X;

Zy(i) = (Y(i) - Mean_Y)/Std_Y;

else

Zx(i) && Zy(i) == 0

end

rowsToKeep = abs(Zx > -2.5 | Zx < 2.5) & (Zy > -2.5 & Zy < 2.5);

OutZScore = [X(rowsToKeep) Y(rowsToKeep) Zx(rowsToKeep) Zy(rowsToKeep)];

X1=X(rowsToKeep);

Y1=Y(rowsToKeep);

figure

plot(X, Y,'b.')

hold on

plot(X1,Y1,'r.')

hold off

grid

If your any comment for my coding?

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Joel Handy 2019-7-16

在 MATLAB Online 中打开

There is a bit of a language barrier so I'm not entirely sure what your question is. The statement you have highlighted will be true when -2.5 <= Zx <=2.5 AND -2.5 <= Zy <=2.5 and rowsToKeep with be the same size as Zx and Zy. You can craft a similar logical statement with whatever conditions you would like. If you would rather the upper limit be 3, the statment woul look like this:

rowsToKeep = (Zx >= -2.5 & Zx <= 3) & (Zy >= -2.5 & Zy <= 3)

I'm using logical indexing in my answer. That is one topic to research for more information.

Joel Handy 2019-7-16