Unrecognized function or variable 'x'.

Question

Emre Can Usengul 2020-4-13

1
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/517602-unrecognized-function-or-variable-x

评论： Stephen23 2024-10-20

function y = Tsin(x,n)
x=input('Degrees: ');
y=input('Terms: ');
%Tsin calculates the sin using Taylor formula.
%Input arguments:
%x The angle in degrees, n number of terms.
z=x*pi/180;
y=0;
for k=0:n-1
    y=y+(-1)^k*z^(2*k+1)/factorial(2*k+1);
end

RUN then

>> Tsin(x, n)
Unrecognized function or variable 'x'.

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Nandini 2022-6-22

编辑：Walter Roberson 2024-10-20

在 MATLAB Online 中打开

PenaltyFactor=100;
LMUpdateRate=0.0100;
AbsoluteTolerance=5.0000e-06;
RelativeTolerance=0.0050;
MaxIterations=1000;
InitialIMFs=zeros(length(x),5);
InitialLM=zeros(length(x)+1,1);
CentralFrequencies= [];
InitializeMethod='peaks';
FFTLength=2*length(x);
NumIMFs= 5;
SignalLength= length(x);
HalfSignalLength=length(x)/2;
MirroredSignalLength=2*length(x);
DataType= 'double';
NumHalfFreqSamples= length(x)+1;
Display= 0;
%%
nfft = FFTLength;
penaltyFactor = PenaltyFactor;
numIMFs = NumIMFs;
relativeDiff = inf;
absoluteDiff = relativeDiff;
tau = LMUpdateRate; % Lagrange multiplier update rate
xr = [x(HalfSignalLength:-1:1); x; x(SignalLength:-1:ceil(SignalLength/2)+1)];
y = fft(xr,FFTLength);
sigFDFull = y; 
% Get half of the bandwidth
sigFD = sigFDFull(1:NumHalfFreqSamples);
initIMFfdFull = fft(InitialIMFs,nfft);
initIMFfd = initIMFfdFull(1:NumHalfFreqSamples,:) + eps; 
IMFfd = initIMFfd;
sumIMF = sum(IMFfd,2);
LM = InitialLM(:); % Lagrange Multiplier
%% Frequency vector from [0,0.5) for odd nfft and [0,0.5] for even nfft
f = (0:(nfft/2))/nfft;
%%  Get the initial central frequencies
x=abs(sigFD);
BW = 2/FFTLength; % bandwidth of signal
minBWGapIndex = 2*BW/f(2);
x(x<mean(x)) = mean(x);
TF = islocalmax(x,'MinSeparation',minBWGapIndex);
pkst = x(TF);
locst = f(TF);
numpPeaks = length(pkst);
% Check for DC component
if x(1) >= x(2)
    pks = zeros(numpPeaks+1,1);
    locs = pks;
    pks(2:length(pkst)+1) = pkst;
    locs(2:length(pkst)+1) = locst;
    pks(1) = x(1);
    locs(1) = f(1);
else
    pks = zeros(numpPeaks,1);
    locs = pks;
    pks(1:length(pkst)) = pkst;
    locs(1:length(pkst)) = locst;
end   
[~,index] = sort(pks,'descend');
centralFreq = 0.5*rand(NumIMFs,1);
% Check if the number of peaks is less than number of IMFs
if length(locs) < NumIMFs
    centralFreq(1:length(locs(index))) = locs;
else
    centralFreq(1:NumIMFs) = locs(index(1:NumIMFs));
end
%%
iter = 0;
f=f';
initIMFNorm = abs(initIMFfd).^2;
normIMF = zeros(size(initIMFfd,1),size(initIMFfd,2));
while (iter < MaxIterations && (relativeDiff > RelativeTolerance ||...
        absoluteDiff > AbsoluteTolerance))   
    for kk = 1:numIMFs
        sumIMF = sumIMF - IMFfd(:,kk);          
        IMFfd(:,kk) = (sigFD - sumIMF + LM/2)./...
            (1+penaltyFactor*(f - centralFreq(kk)).^2);
        normIMF(:,kk) = abs(IMFfd(:,kk)).^2;
        centralFreq(kk) = (f.'*normIMF(:,kk))/sum(normIMF(:,kk));           
        sumIMF = sumIMF + IMFfd(:,kk);            
    end
    LM = LM + tau*(sigFD-sumIMF);
    absDiff = mean(abs(IMFfd-initIMFfd).^2);
    absoluteDiff = sum(absDiff);
    relativeDiff = sum(absDiff./mean(initIMFNorm));
    
    % Sort IMF and central frequecies in descend order
    % In ADMM, the IMF with greater power will be substracted first
    [~,sortedIndex] = sort(sum(abs(IMFfd).^2),'descend');
    IMFfd = IMFfd(:,sortedIndex);
    centralFreq = centralFreq(sortedIndex(1:length(centralFreq)));
    initIMFfd = IMFfd;
    initIMFNorm = normIMF;  
    iter = iter + 1;
    
end
%%--------------------- Step 08 --------------------------------
%% Convert to time domain signal     
% Transform to time domain
IMFfdFull = complex(zeros(nfft,numIMFs));
IMFfdFull(1:size(IMFfd,1),:) = IMFfd;
if ~mod(FFTLength,2)
    IMFfdFull(size(IMFfd,1)+1:end,:) = conj(IMFfd(end-1:-1:2,:));
else
    IMFfdFull(size(IMFfd,1)+1:end,:) = conj(IMFfd(end:-1:2,:));
end
[~,index] = sort(centralFreq,'descend');   
%%
z=IMFfdFull(:,index);
xr = real(ifft(z,FFTLength));
IMFs_without_inbuild = xr(HalfSignalLength+1:MirroredSignalLength-HalfSignalLength,:);
residual_without_inbuild = PPGblr1 - sum(IMFs_without_inbuild,2);

Juan David 2024-4-6

移动：Voss 2024-4-6

在 MATLAB Online 中打开

% Función para calcular el valor de Lagrange
function y = lagrange2(X, Y)
n=length(X);
sym x;
for i=1:n
    w=1;
    for j=1:n
        if j~=1
           w = w * (x - X(j)) / (X(i) - X(j));
        end
    end
  
end
 y = 0;
for i=1:n
    y = y + w(i) * Y(i);
end
y=simplify(expand(ecuacion));
end
RUN then
Unrecognized function or variable 'x'.
Error in lagrange2 (line 10)
           w = w * (x - X(j)) / (X(i) - X(j));
 

Voss 2024-4-6

Instead of

sym x;

use

syms x;

or

x = sym('x');

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Answer 1

Adam Danz 2020-4-13

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/517602-unrecognized-function-or-variable-x#answer_425817

编辑：Adam Danz 2020-4-13

在 MATLAB Online 中打开

You need to define the input variables. You cannot simply run a function that has undefined input variables.

x = 45
n = 8
Tsin(x,n)

____________________________________

Copy of question:

function y = Tsin(x,n)
x=input('Degrees: ');
y=input('Terms: ');
%Tsin calculates the sin using Taylor formula.
%Input arguments:
%x The angle in degrees, n number of terms.
z=x*pi/180;
y=0;
for k=0:n-1
    y=y+(-1)^k*z^(2*k+1)/factorial(2*k+1);
end

RUN then

>> Tsin(x, n)
Unrecognized function or variable 'x'.

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Dylan Radey 2021-3-3

can't define a variable for fiding a root :\

Adam Danz 2021-7-29

@Dylan Radey I don't know what that means. All variables are defined either directly by the user or from computations within the function/script.

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Answer 2

Yuyang Mao 2021-8-5

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/517602-unrecognized-function-or-variable-x#answer_761397

I got the same problem before.

Explaination: Please make sure that you have add your function to the path!

solution:

Click run, it jumps out a window
click 'add to path', is shows error in red color which is fine
now give the name of your function again, in your case is 'Tsin(x,n)'

And this should work.

Best,

Yuyang

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Adam Danz 2021-8-9

Good advice. However, in this question, the function name is Tsin but the unrecognized variable name is x.

Jordan Wood 2021-8-10

Need to reinput the values you want for x and n in the command window

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Answer 3

SUNIL KUMAR 2024-10-20

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/517602-unrecognized-function-or-variable-x#answer_1534445

在 MATLAB Online 中打开

syms x
solve('x+3=4',x)
Error using sym/solve>getEqns (line 418)
List of equations must not be empty.

Error in sym/solve (line 226)
[eqns,vars,options] = getEqns(varargin{:});

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Answer 4

SUNIL KUMAR 2024-10-20

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/517602-unrecognized-function-or-variable-x#answer_1534455

在 MATLAB Online 中打开

f=inline('x^2','x')
f =

     Inline function:
     f(x) = x^2
diff(f(x),x)
Unrecognized function or variable 'x'.

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Stephen23 2024-10-20

在 MATLAB Online 中打开

syms x
f = x^2
diff(f,x)

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Unrecognized function or variable 'x'.

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