如何在Matlab中从绘图中截取部分数据

Question

我只是想在MATLAB中删除部分数据，例如:如果我点击轴上的两个点，它会在我点击x轴后切割元素。我会张贴我的代码和图片进一步的细节提前谢谢你

load sample.mat
X = sample.current;
X1 = sample.voltage;
Ts = 0.01;
Fs = 1/Ts;
Fm = Fs/2;
Fc = 2;
N =10;
d = fdesign.lowpass('N,Fc',N,Fc,Fs);
designmethods(d);
Hd = design(d);
%fvtool(Hd)
%X is a variable form csv
%X1 is a variable from csv
output = filter(Hd,X);
output1 = filter(Hd,X1);
figure;
plot(X,X1,'-g');
hold on
plot(output, output1,'r');
hold off
legend('raw signal','filtered signal')
grid on
x = output, output1;
y = output1;
figure
subplot(2,1,1)
plot(x,y,'r');
title('Original plot');
uiwait(msgbox('Select an x-value from which to crop','modal'));
[x_user ~] = ginput(1); % Let the user select an x-value from which to crop.
x(x>x_user) = [];
subplot(2,1,2);
plot(x,y,'r');
title('New plot with cropped values');
xlim([min(x(:)) max(x(:))]);

输入图片描述

Answer 1

*将此作为格式代码的答案。

如果只有一个图形，你可以使用"画笔/选择数据"选择要删除的点(图中菜单栏上带有红色方块的笔刷图标)选择想要删除的数据，然后按下删除键。

如果你想用代码来做，你可以试着找到信号在X上开始减少的点的索引，使用如下命令:

% Find the index where X starts to decrease
maxIndex = find(data.x == max(data.x));
% In case of multiple indexs, ensure we get the first one
maxIndex = maxIndex(1);
% Copy data to new vector 
saveData.x = data.x(1:maxIndex);
saveData.y = data.y(1:maxIndex);

如果你想使用用户的点击位置，你可以使用find来定位点击后的第一个元素的索引:

% Get the coords of the first click
userFirstClick = ginput(1);
% Get the X component of the coords
xCoordInit = userFirstClick(1);
% Locate the index of the first element that is greater than 
% the xCoord
firstXIndex = find(data.x >= xCoordInit);
% In case of multiple indexs, ensure we get the first one
firstXIndex = firstXIndex(1);
% Do the same to get the final index
userSecondClick = ginput(1);
xCoordFinal = userSecondClick(1);
finalXIndex = find(data.x > xCoordFinal);
finalXIndex = finalXIndex(1)-1;
% -1 because data.x(finalXIndex) is already greater than xCoordFinal
% Copy data to the new vector
saveData.x = data.x(firstXIndex:finalXIndex);
saveData.y = data.y(firstXIndex:finalXIndex);

然后绘制saveData。

---

编辑

在我之前的代码中有一个错字，这里你有一个功能齐全的例子，你只需要点击你想要裁剪的两个点。

function cropSine()
% create a period of a Sine to initialize our data
data.x = -pi*3:0.01:pi*3;
data.y = sin(data.x);
% we make it loop back just as in your picture
data.x = [data.x,data.x(end:-1:1)];
data.y = [data.y, -data.y*0.5+5];
% create a figure to show the signal we have just created
figure
% create the axes where the data will be displayed
mainAx = axes();
% Draw our fancy sine!
plot(data.x, data.y, 'b-', 'Parent', mainAx);

% Request the initial position to crop
userFirstClick = ginput(1);
% Get the index of the nearest point
initIndex = getNearest(userFirstClick, data);

% Do the same to get the final index
userSecondClick = ginput(1);
% Get the index of the nearest point
finalIndex = getNearest(userSecondClick, data);


% check if its a valid point
if isempty(initIndex) || isempty(finalIndex)
disp('No points in data vector!');
return;
end

% Ensure that final index is greater than first index
if initIndex > finalIndex
tempVal = initIndex;
initIndex = finalIndex;
finalIndex = tempVal;
end

% Copy the data that we want to save into a new variable
saveData.x = data.x(initIndex:finalIndex);
saveData.y = data.y(initIndex:finalIndex);
% Plot the cropped data in red!
hold(mainAx, 'on');
plot(saveData.x, saveData.y, 'r-', 'Parent', mainAx);
hold(mainAx, 'off');
end
function nearestIndex = getNearest(clickPos, vector)
nearestIndex = [];
numPoints = length(vector.x);

if numPoints == 0
return;
end

nearestIndex = 1;

minDist = calcDist(vector.x(1), vector.y(1), clickPos(1), clickPos(2));

for pointID = 1:numPoints
dist = calcDist(vector.x(pointID), vector.y(pointID), clickPos(1), clickPos(2));
if dist < minDist
nearestIndex = pointID;
minDist = dist;
end
end
end
function dist = calcDist(p1x, p1y, p2x, p2y)
dist = sqrt(power(p1x-p2x,2)+power(p1y-p2y,2));
end