如何从 Matlab 中的绘图中截取部分数据

Question

我只是想在 MATLAB 中截取部分数据，例如： 如果我点击轴上的两个点，它会在我点击后相对于 x 轴切割元素。我将发布我的代码和图片以获取更多详细信息 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(:))]);

enter image description here

Answer 1

*将此作为格式代码的答案发布。

如果它只有一个图形，您只需选择要删除的点，使用“画笔/选择数据”（图菜单栏上带有红色方块的画笔图标）选择您想要删除的数据消失，然后按删除键。

如果您想使用代码来执行此操作，您可以尝试使用以下方法找到信号开始在 X 上减少的点的索引：

% 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);

如果要使用用户的点击位置，可以使用 find 定位点击后第一个元素的索引：

% 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);

然后只需绘制 saveData。

---

编辑

我之前的代码有错别字，这里有一个功能齐全的示例，您只需单击要裁剪的两个点即可。

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