Rotating X & Y Data

Question

Tania 2022-9-20

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1808590-rotating-x-y-data

评论： Star Strider 2022-9-27

Hello

I am trying to rotate GPS data, that has been con verted into X & Y coordintes to dsplay lengthwy along the Y axis strting at 0,0

I'm trying to rotate data in a 6135 x 15 table, where the data is layed out as follows 6135 data points of coordintes seperted into X & yXcolumns for each person.

Time I Person 1 x I Person 1 y I Person 2 x I Person 2 y I Person 3 x I Person 3 y .....etc

I would like to rotate this date to run length way along the Y axis. Each line represents data for a different person (7 in total):

Is there a way to rotate a large table of X & Y coordinates.

Thank you in advance for your help!

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Answer 1

Star Strider 2022-9-20

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1808590-rotating-x-y-data#answer_1057120

See if the rotate function will work.

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Tania 2022-9-21

Hey,

Thanks for this, it’s still not working. I'm receiving an error message, indices on the left side are not compatible with the right side.

I have graphed an X & Y Scatter plot displaying 6135 individual X & Y data points for 7 people (each line representing a different person).

I originally converted the ray Lat/Lon co-ordinates to X & Y coordinates using the following:

[x1,y1]= wgs2utm((data1(:,2)),(data1(:,3))) % I repeated this for each person

I then plotted each converted X & Y data point onto the graph above using the following code:

PlotGPS = scatter(Newdata(:,1),Newdata(:,2)); %Plots all the GPS data in a scatter to select 4 grid coordinates%

hold on

scatter(Newdata(:,3),Newdata(:,4));

scatter(Newdata(:,5),Newdata(:,6));

scatter(Newdata(:,7),Newdata(:,8));

scatter(Newdata(:,9),Newdata(:,10));

scatter(Newdata(:,11),Newdata(:,12));

scatter(Newdata(:,13),Newdata(:,14));

hold off

From here I used:

[PlotGPS] = ginput(4)

To create a boundary around the data points representing an (almost rectangular) field (shown by small light blue circles).

I then used the below code to rotate the boundary

Boundary = PlotGPS([2 4 3 1 2],:);

Boundlong = PlotGPS(4,:) - PlotGPS(2,:); % Length of line - long line

Boundshort = PlotGPS(1,:)- PlotGPS(2,:); % Width of line - short line

%% Rotational Matrix

theta = atan2(Boundlong(2),Boundlong(1)); % theta is in radians

R = [cos(theta) -sin(theta); sin(theta) cos(theta)]; % rotation matrix

BoundR = Boundary*R; %Rotate the field

This worked, however when I tried to apply the same code to the data, because of the large volume of X & Y data points, it did not work.

Is there a way to use the boundary to assist with rotating the X & Y data?

Thanks for your help

Star Strider 2022-9-23

在 MATLAB Online 中打开

Using your posted data —

LD = open(websave('XY Data(3165,2)','https://www.mathworks.com/matlabcentral/answers/uploaded_files/1131570/XY%20Data%20(6135,2).mat'));

XY_P1 = LD.XY_P1;

x = XY_P1(:,1);

y = XY_P1(:,2);

B = [x ones(size(x))] \ y;

slope = B(1) % Line Slope

slope = 1.3159

angd = atand(slope) % Arctangent Of Slope In Degrees

angd = 52.7676

ang2d = atan2d(mean(diff(y)), mean(diff(x))) % Arctangent Option Using 'atan2d'

ang2d = 55.1069

figure

p(1) = plot(x, y);

grid

axis('equal')

title('Original')

figure

p(1) = plot(x, y);

grid

axis('equal')

rotate(p(1), [0 0 1], -angd) % Rotate Line Using Negative Arctangent Of Calculated Slope

title('Rotated To Parallel X-Axis')

So the rotate function appears to work here.

This is the best I can do with these data. Fortunately, the data here appear to be in a straight line, so this appears to be obvious. If they are not in a relatively straight line, the code should still work, although it might not be as obvious, since it will use the linear regression slope value to do the rotation.

Using atan2d to calculate the slope angle could be more robust (I included an option using it), however if the angles are restricted to the first two quadrants, atand should work well enough.

NOTE — The rotation is with respect to the Z axis. This is not intuitive (at least to me), however it produces the desired result.

.

Tania 2022-9-27

Thanks for your help with this!

Star Strider 2022-9-27

As always, my pleasure!

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Answer 2

KSSV 2022-9-20

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1808590-rotating-x-y-data#answer_1057085

在 MATLAB Online 中打开

p1 = rand(2,1) ;

p2 = rand(2,1) ;

%%rotation matrix

th = 90*pi/180 ;

R = [cos(th) -sin(th) ;sin(th) cos(th)] ;

%%rotate points

pr2 = R*p2 ;

figure

hold on

plot([p1(1) p2(1)],[p1(2) p2(2)] ,'r') ;

plot([p1(1) pr2(1)],[p1(2) pr2(2)] ,'b') ;

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Tania 2022-9-23

Hello

I've attempted to rotate my data using the below code:

Note xy2 is the data set (6135x2 matrix)

theta = atan2(xy2(:,2),xy2(:,1));

R = [cos(theta) -sin(theta); sin(theta) cos(theta)];

RR = R(1:6135,:).*xy2;

As R is double the length of the xy2 data set I select the first 6135 rows in enable multiplication for the rotated (RR) dataset.

The below graph is the original xy2 dataset in a scatter:

This next graph below is of the rotated data RR

Instead of rotating it has flipped the data set. I need the data rotted so it runs longitudinally along the Y axis.

Without guessing the theta angle is there a way to correctly determine the rotation angle I need?

Thanks is advance for your help.

Tania 2022-9-23

As a reference (continued from comment above):

I originally converted the ray Lat/Lon co-ordinates to X & Y coordinates using the following:

[x1,y1]= wgs2utm((data1(:,2)),(data1(:,3))) % I repeated this for each person

I then plotted each converted X & Y data point onto the graph above using the following code:

PlotGPS = scatter(Newdata(:,1),Newdata(:,2)); %Plots all the GPS data in a scatter to select 4 grid coordinates%

hold on

scatter(Newdata(:,3),Newdata(:,4));

scatter(Newdata(:,5),Newdata(:,6));

scatter(Newdata(:,7),Newdata(:,8));

scatter(Newdata(:,9),Newdata(:,10));

scatter(Newdata(:,11),Newdata(:,12));

scatter(Newdata(:,13),Newdata(:,14));

hold off

From here I used:

[PlotGPS] = ginput(4)

To create a boundary around the data points representing an (almost rectangular) field (shown by small light blue circles).

I then used the below code to rotate the boundary

Boundary = PlotGPS([2 4 3 1 2],:);

Boundlong = PlotGPS(4,:) - PlotGPS(2,:); % Length of line - long line

Boundshort = PlotGPS(1,:)- PlotGPS(2,:); % Width of line - short line

%% Rotational Matrix

theta = atan2(Boundlong(2),Boundlong(1)); % theta is in radians

R = [cos(theta) -sin(theta); sin(theta) cos(theta)]; % rotation matrix

BoundR = Boundary*R; %Rotate the field

This worked, (see above).

From my last post I'm now able to rotate, the X & Y dta points, hopwever as you can see in my last post its not rotating correctly.

Is there a way to use the boundary reference information to rotate my X & Y data?

Thanks in advance for your help/insight.

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