Matlab 绘制信号的导数

我在编码方面遇到了一个问题。我在一个图中有多个图。我得到的所有图都是正确的，但不幸的是，导数图在图中甚至不可见。有人能帮忙吗。。提前谢谢

close all
clear all
clc
load('2019-01-31-structTFMRI-Proband04-Ivan.mat')

fs=structTFMRI.SigInfo.fs; %Sampling frequency in Hz
%PlotLead = 10;
%ECG lead to plot (only used for 12-lead ECG)

%% 12-lead ECG (Outside and Inside MRI)
ECGOutSingle = structTFMRI.ECGMRI.ECG12OutSingle; %820 Samples per beat (~800ms), 120 beats, 12 leads
ECGInSingle = structTFMRI.ECGMRI.ECG12InSingle; %820 Samples per beat (~800ms), 182 beats, 12 leads

%Plot the data
figure; 
hold on
for PlotLead=4:4
    t=(0:1:length(ECGOutSingle(:,1,PlotLead))-1)/fs; %Time vector for plot to have x-axis in seconds
    %plot(t,ECGOutSingle(:,1,PlotLead))
    %plot(t,ECGInSingle(:,1,PlotLead))
    plot(t,ECGInSingle(:,1,PlotLead)-ECGOutSingle(:,1,PlotLead))  %MHD signal

    MHD = ECGInSingle(:,1,PlotLead)-ECGOutSingle(:,1,PlotLead);
    x = 1:length(ECGInSingle);
    [Zi,Zi_idx,Xi,Xi_idx,Bi,Bi_idx] = getZXB(MHD);  
    y = diff(MHD);
    z = diff(x);
    plot(z,y); 
    plot(x,MHD);
    plot(x(Bi),MHD(Bi),'r*');
    plot(x(Xi),MHD(Xi),'g*');
    plot(Zi_idx,Zi,'b*');
end

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您正在绘制MHD的导数与x的导数：

相反，绘制MHD对x的导数：

diffx是一个具有所有相同值的数组。因此，所有y值都沿x轴绘制在同一位置。

所有值都是NaN吗？因为您没有提供，所以无法判断，但是没有绘制NaN值，所以这是一个可能的诊断。

y = diff(MHD);
z = diff(x);
plot(z,y); 

y = diff(MHD);
plot(x,y);