"ans" variable function output unwanted

Hi All,

I wrote a function in matlab in order to process some data. The function works fine and the results are as I want.

However, the function generates (unexpectatly) a variable "ans" which correspond to the first output of the function (time)

See my code below

I know that by default when a function is created all the first output value is returned. How can I avoid that (in order to leave clear the workspace)?

Thanks all for you help

G

%%Time Domain and Logging Frequency

time = Data_Raw(:,1)/1000; % 1st Colum is logging time in ms (from Arduino)

Fs = 1/mean(diff(time)); % Actual sample frequency (Hz)
TO_USER = ['The Real Logging Time of the system is in average ', num2str(Fs), ' Hz'];
clc
disp(TO_USER)
clear TO_USER
%%From Analog to Acceleration in g

ax  = 3.5/(1023/2) * Data_Raw(:,2) - 3.5;   % Accelerometer range -3.5g +3.5g
ay = 3.5/(1023/2) * Data_Raw(:,3) - 3.5;   % Accelerometer range -3.5g +3.5g
az = 3.5/(1023/2) * Data_Raw(:,4) - 3.5;   % Accelerometer range -3.5g +3.5g

%%Smooting the Accelerations

Ax = feval(fit(time, ax,  'smoothingspline'), time);  % with parameter set to Auto
Ay = feval(fit(time, ay,  'smoothingspline'), time);
Az = feval(fit(time, az,  'smoothingspline'), time);
clear ax ay az;

%%HIGH PASS FILTER to compensate for the iniail position of the accelerometer (not always in level)

% filter definition
%Fc = 0.2; % cutoff frequency (Hz)
%[B,A]=butter(5,Fc/(Fs/2),'high');  % calcultate the filter numerator and denominator coeffients          

%Ax_0 = filtfilt(B,A,Ax); % apply the filter defined in the lines above
%Ay_0 = filtfilt(B,A,Ay);
%Az_0 = filtfilt(B,A,Az);

%clear A; clear B; clear Fc; clear Fs;

%    THE HIGH PASS FILTER MODIFY THE DATA TOO MUCH -  THIS METHOD DOES NOT
%    SEEMS APPROPRIATE, then the solution is zeroing taking the average off

%%Zeroing by taking off the average

Ax_zeroed = Ax - mean(Ax);
Ay_zeroed = Ay - mean(Ay);
Az_zeroed = Az - mean(Az);

%%Plotting

% Create figure
figure1 = figure;

% Create axes
axes1 = axes('Parent',figure1,'XTickLabel',{'','','','','',''},'Position',[0.11843187660668 0.682981090100111 0.774884318766067 0.309749136467419]);
box(axes1,'on');
hold(axes1,'all');

% Create plot
plot(time,Ax_zeroed,'Parent',axes1,'DisplayName','Longitudinal g');

% Create axes
axes2 = axes('Parent',figure1,'XTickLabel',{'','','','','',''},'Position',[0.118431876606679 0.364756889268502 0.774884318766067 0.309749136467419]);
box(axes2,'on');
hold(axes2,'all');

% Create plot
plot(time,Ay_zeroed,'Parent',axes2,'Color',[0 0.5 0],'DisplayName','Lateral g');

% Create ylabel
ylabel('Acceleration (g)','FontSize',16);

% Create axes
axes3 = axes('Parent',figure1,'XTick',[0 50 100 150 200 250],'Position',[0.118431876606679 0.0452654481856993 0.774884318766067 0.309749136467419]);
box(axes3,'on');
hold(axes3,'all');

% Create plot
plot(time,Az_zeroed,'Parent',axes3,'Color',[1 0 0],'DisplayName','Vertical g');

% Create xlabel
xlabel('Time (sec)','FontSize',14);

% Create legend
legend(axes1,'show');

% Create legend
legend(axes2,'show');

% Create legend
legend(axes3,'show');

%%Saving

% TO BE COMPLETED
end

[Azzi Abdelmalek]

Your code does not represent a function

Answer 1

[Giuseppe Naselli]

Found the problem and it is very stupid (and embarassing)

The function is absolutely fine. I called the function with the command

[time,Ax,Ay,Az] = data_acq(varname)

but as any other function in Matlab, if I do not use the ";" like

[time,Ax,Ay,Az] = data_acq(varname);

Matlab automatically provides the first output of the function.

SOrry for populating this form with this stupid questions

[Image Analyst]

As my answer said (which you should have accepted instead of this one). Though I'm still confused because what you said is not true: "as any other function in Matlab, if I do not use the ";" Matlab automatically provides the first output of the function." Not true - it reports all of them to the command window, not just the first one. Look:

function test3
[a,b,c] = f()

function [a,b,c] = f()
a=1;
b=2;
c=3;

In the command window you see

>> test3
a =
     1
b =
     2
c =
     3

Moreover, the variables are given their actual names, not the generic "ans" so that's why I'm puzzled by your "Answer".

Answer 2

[Jan]

What exactly is the problem? That the command window contains some output or that the variable ans is created?

• For the first case, set a semicolon behind the command, which calls the function. Example:

sin(2)        % ans = 0.9093   appears
sin(2);       % nothing appears

• For the 2nd case, you can and should avoid to create an output, if you do not want to obtain it in the caller:

function NoOutput(in1)
your operations here...

If your function should reply nothing only if no outputs are wanted from the caller:

function Out = OutputOnDemandOnly(In)
Reply = sin(In);
if nargout ~= 0
  Out = Reply;
end

Now try:

OutputOnDemandOnly(2)
OutputOnDemandOnly(2);
a = OutputOnDemandOnly(2)
a = OutputOnDemandOnly(2);

Answer 3

[Image Analyst]

Put a semicolon at the end of the line to suppress display of the ans output to the command window.

[Giuseppe Naselli]

Hi and thanks for your answer.

in which line you mean?

I think I have already a semicolon everywhere there is a command

G

[Image Analyst]

Step through your code one line at a time in the debugger to see where it gets produced. http://blogs.mathworks.com/videos/2012/07/03/debugging-in-matlab/