MATLAB函数无法识别quad函数错误

Matlab报错：函数或变量’’无法识别

运行结果及报错内容

一共出现两个错误：
1.函数或变量 'QUAD' 无法识别。

在出现QUAD无法识别后，我在E:\Matlab 2020b\toolbox\matlab\funfun路径下找到了quad.m函数，将其改为QUAD.m后，错误1消失，但紧接着出现错误2
2.函数或变量 'CVintgrd' 无法识别。
出错 QUAD (第 67 行)
y = f(x, varargin{:});

以下代码为全部代码

%LOW and/or HIGH-frequency p-type MOS-C C-V CHARACTERISTICS
%Subprogram CVintgrd is a run-time requirement.

%Initialization and Inputformat compact
close
clear
s=menu('Choose the desired plot','Low-f C-V','High-f C-V','Both');
NA=input('Please input the bulk doping in /cm3, NA=');
xo=input('Please input the oxide thickness in cm,xo=');
xmin=input('Specify VGmin(volts), VGmin=');
xmax=input('Specify VGmax(volts),VGmax=');
global UF

%Constants and Parameters
e0=8.85e-14;
q=1.6e-19;
k=8.617e-5;
KS=11.8;
KO=3.9;
ni=1.0e10;
T=300;
kT=k*T;

%Computed Constants
UF=log(NA/ni);
LD=sqrt((kT*KS*e0)/(2*q*ni));

%Gate Voltage Computation
US=UF-21:0.5:UF+21;
F=sqrt(exp(UF).*(exp(-US)+US-1)+exp(-UF).*(exp(US)-US-1));
VG=kT*(US+(US./abs(US)).*(KS*xo)/(KO*LD).*F);

%Low-frequency Capacitance Computation
DENOML=exp(UF).*(1-exp(-US))+exp(-UF).*(exp(US)-1);
WL=(US./abs(US)).*LD.*(2*F)./DENOML;
cL=1.0./(1+(KO*WL)./(KS*xo));

%High-frequency Capacitance Computation
if s~=1
    jj=length(US);
    nn=0;
    for ii=1:jj,
        if US(ii)<3,
            elseif nn==0,
            INTG=QUAD('CVintgrd',3,US(ii),0.001);
            nn=1;
            else
            INTG=INTG+QUAD('CVintgrd',US(ii-1),US(ii),0.001);
            end
        if US(ii)<3,
            cH(ii)=cL(ii);
            else
            d=(exp(US(ii))-US(ii)-1)./(F(ii).*exp(UF).*INTG);
            DENOMH=exp(UF).*(1-exp(-US(ii)))+exp(-UF).*((exp(US(ii))-1)./(1+d));
            WH=LD.*(2*F(ii))./DENOMH;
            cH(ii)=1.0./(1+(KO*WH)./(KS*xo));
            end
    end
else
end

%Plotting the Result
if s==1,
plot(VG,cL);
elseif s==2,
plot(VG,cH);
else
plot(VG,cL,'--',VG,cH);
text(0.8*xmin,.17,'___Low-f','color',[1,1,0]);
text(0.8*xmin,.12,'___High-f','color',[1,0,1]);
end
axis([xmin,xmax,0,1]);
text(0.8*xmin,.27,['NA=',num2str(NA),'/cm3']);
text(0.8*xmin,.22,['xo=',num2str(xo),'cm']);
xlabel('VG(volts)');ylabel('C/CO');grid

CVintgrd
function [y] = cvintegrand(U)
global UF
F=sqrt(exp(UF).*(exp(-U)+U-1)+exp(-UF).*(exp(U)-U-1);
y=(1-exp(-U)).*(exp(U)-U-1)./(2*F.^3);