Invalid use of operator

Please help me!. I have a problem with this code. When I execute this program. The result is invalid use of operator.

WorkName='Battery';             % work results are saved by WorkName
TimeUnit='weeks';                                    % time unit name
dt=5;                                   % time interval (five weeks) 
measuData=[1.0000 0.9351 0.8512 0.9028 0.7754 0.7114 0.6830 0.6147 ...
    0.5628 0.7090]'; % measured data at every time intervals (k1 x 1)
thres=0.3;                  % threshold - critical value
ParamName=['x'; 'b'; 's'];      % model parameters' name to be estimated
initDisPar=[0.9 1.1; 0 0.05; 0.01 0.1]; 
% probability parameters of initial distribution, pxq
% (p: num. of unknown param, q: num. of probability param)
n=5e3;                                                % number of particles
signiLevel=5;                        % significance level for C.I and P.I
%==========================================================================
% % % PROGNOSTICS using PARTICLE FILTER
p=size (ParamName,1);
for j=1:p;                                      % Initial Distribution
    param(j,:)=unifrnd(initDisPar(j,1),initDisPar(j,2),1,n); 
    ParamResul(j,:)=[ParamName(j,:) 'Resul'];
    eval([ParamResul(j,:) '=param(j,:);']);
end;
kl=length(measuData); k=1;          % Update Process or Prognosis
if measuData (end)-measuData(1)<0; cofec=-1; else cofec =1; end
while min(eval([ParamResul(1,:) '(k,:)'])*cofec)<thres*cofec; k=k+1;
    % stepl. predlotion (prior)
    paramPredi=param;
    for j=1:p; eval([ParamName(j,:) '=paramPredi(j.:);']); end 
    paramPredi(1,:)=...%====== PROBLEM DEFINITION: MODEL DEFINITION=============
        exp(-b.*dt).*x;
    %==========================================================================
    if k<=k1                          %                        (Update Process)
        % step2. update (likelihood)
        like1=normpdf(measuData(k),paramPredi(1,:),paramPredi(end,:));
        % step3. resampling
        cdf=cumsum(like1)./max(sum(likel));
        for i=1:n;
            u=rand;
            loca=find(cdf >= u); param(:,i)=paramPredi(:,loca(1));
        end;
    else                                              % (Prognosis)
        param=paramPredi;
    end
    for j=1:p; eval([ParamResul(j,:) '(k,:)=param(j,:);']); end;
    if k>k1;
        eval([ParamResul(1,:) '(k,:)=normrnd(param(1,:),param(end,:));']);
    end
end
% % % POST-PROCESSING
time=[0:dt:dt*(k-1)]';                                   % RUL Calculation
perceValue=[50 signiLevel 100-signiLevel];
for i=1:n;
    loca=find(eval([ParamResul(1,:) '(:,i)'])*cofec>=thres*cofec);
    RUL(i)=time(loca(1))-time(k1);
end;
RULPrece=prctile(RUL',perceValue);
figure; set(gca,'fontsize',14); hist(RUL,30);       % RUL Results Display
xlim([min(RUL) max(RUL)]);
xlabel(['RUL' ' (' TimeUnit ')']); 
titleName=['at ' num2str(time(k1)) ' ' TimeUnit]; title(titleName)
fprintf('\n # Percentiles of RUL atg weeks \n', time(k1))
fprintf('\n %g, median: %g, %gprct: %g \n', perceValue(2), ...
    RULPerce(2), RULPerce(1), perceValue(3), RULPerce(3))
Name=[WorkName ' at ' num2str(time(k1)) '.mat']; save(Name);  % Work Save

The following is the error that appears in the command window

>> Prognosis

Error using Prognosis

Invalid use of operator.

[Sarvesh Kale]

The error is in the following line

p=size (ParamName,1);
for j=1:p;                                    
    param(j,:)=unifrnd(initDisPar(j,1),initDisPar(j,2),1,n); 
    ParamResul(j,:)=[ParamName(j,:) 'Resul'];
    eval([ParamResul(j,:) '=param(j,:);']); % this line gives error 
end;

what are you exactly trying to do with the eval there ?

Answer 1

[Jan]

The old problem: Strange methods to define names of variables dynamically using eval() demands for even stranger methods to access these variables later on. This is the typical shot in the own knee. See: FAQ: Why and how to avoid EVAL .

Use dynamic field names instead:

% Replace:
%    ParamResul(j,:)=[ParamName(j,:) 'Resul'];
%    eval([ParamResul(j,:) '=param(j,:);']);
% by:
Resul.(ParamName(j)) = param(j,:);

Afterwards all eval calls can be replaced by using the fields directly. This makes the code cleaner, easier to debug and to maintain and much faster.

[Ikhsan Romli]

Sorry, Mr. Jan. I don't understand how to change all the other evals. Can you help me to fix this code until the result is not error. Thank you.

[Jan]

I cannot fix the errors in your code without seeing the code. So please post zu current version of your code.

Changing

eval([ParamResul(j,:) '=param(j,:);']);

to

Resul.(ParamName(j)) = param(j,:);

seems to be more or less trivial, so I cannot guess, which problems you have with it.

[Ikhsan Romli]

Here I attach my version of the code