Error using rand Size inputs must be integers. Error in make_sct (line 53) x=x_range*​(rand(1,N)​-0.5);

% Example of use of the Field II program running under Matlab. % % This program generates the positions for blood and tissue scatterers - lying % at some distance from the skin and at some angle relative to the direction of % the transducer and emitted pulse. % The program takes into account the motion due to pulsation and respiration.

% Example by Malene Schlaikjer and Jrgen Arendt Jensen, January 15, 1999.

% Initializing parameters

f0=3.75e6; % Transducer center frequency [Hz] fs=105e6; % Sampling frequency [Hz] c=1540; % Speed of sound [m/s] lambda=c/f0; % Wavelength element_height=15/1000; % Height of elements in transducer [m] No_elements=60; % Number of physical elements kerf=0.03/1000; % Kerf [m] - explain focus=[0 0 40]/1000; % Fixed focal point [m] fprf = 3.5e3; % Pulse repetition frequency

% Set the seed of the random generator

randn('seed',sum(100*clock));

% Initialize the ranges for the scatterers.

x_range=0.012; % x range for the scatteres [m].

z_range=0.030; % z range for the scatteres [m].

y_range=0.015; % y range for the scatteres [m].

z_depth=30/1000; % depth of center of the scatteres [m].

R=0.004; % Radius of blood vessel [m].

Rwv=0.0003+R; % Radius of blood vessel and vessel wall.

R_scanrange=0.020; % Value of scan range.

% Set the number of scatterers. Roughly 10 scatterers per resolution cell.

N=10*(x_range/(5*lambda))*(y_range/(5*lambda))*(z_range/(2*lambda)) disp([num2str(N),' Scatteres'])

% Generate the coordinates and amplitude. Amplitude has a Gaussion distribution. % Coordinates are rectangular within the range.

x=x_range*(rand(1,N)-0.5); y=y_range*(rand(1,N)-0.5); z=z_range*(rand(1,N)-0.5);

% Generating scatterers that is resembles the vessel wall

N_ex=1000;

x_ex=x_range*(rand(1,N_ex)-0.5);

radius_ex=rand(1,N_ex)*0.0003+R; angle_ex=(rand(1,N_ex)-0.5)*2*pi;

[y_ex,z_ex]=pol2cart(angle_ex,radius_ex);

% All scatterer positions

x=[x x_ex];

y=[y y_ex];

z=[z z_ex];

% Assign an amplitude and a velocity for each scatterer.

v0=0.5; % Largest velocity of scatteres [m/s]

blood_to_stationary=0.1; % Ratio between amplitude of blood to stationary % tissue. amp=randn(N+N_ex,1); % Initializing amplitudes.

Tprf=1/fprf; % Time between pulse emissions [s]. Nshoots=fprf; % Number of shoots.

% Loading of file containing blood velocity profiles generated from Womersley's % velocity model.

 eval('load velocity;');

% Estimation of dilation values due to pulsation for one cycle

cyclesteps=0:Tprf:(1-Tprf);
deltaR_puls=(1.05*sin(pi*cyclesteps).*exp(-2.7*cyclesteps)/1000);

% Estimation of dilation values due to breathing

timeresp=0:Tprf:(5-Tprf);
movResp=abs(0.0004*sin(2*pi*timeresp/9));

for m=1:Nshoots
  m

[angleP,radius]=cart2pol(y,z);

% Adjustment of radius as a function of time is included due to the % movement of the vessel wall because of the pulsation of the heart. % The change in radius of scatterer - relative to center of vessel - % depends on whether the scatterer is lying within or outside the vessel, % and the change is damped the further away from the vessel center the % scatterer is positioned.

timePulse=mod(m,fprf);

   if timePulse==0
     timePulse=fprf;
   end  

within_vessel=radius<R;

radiusN=radius+deltaR_puls(timePulse)*(radius.*within_vessel/R)...
   +deltaR_puls(timePulse)*(1-radius./R_scanrange).*(1-within_vessel);

Rnew=R+deltaR_puls(timePulse);

[yP,zP]=pol2cart(angleP,radiusN);

r_rel=radiusN/Rnew;
r_rel_index=round(r_rel/0.0025)+1;

% Index that controls assignment of the velocities obtained from % from the velocity profile matrix. % In the matrix the velocities are ordered according to relative radius % - equal to : radius_scatterer/radius_of_vessel. % Index 401 indicates velocity=0 m/s.

index_final=r_rel_index.*within_vessel+(1-within_vessel)*401;

% Assign new velocity for each scatterer.

velocity=profiles(index_final,timePulse)';

ampN1=amp.*(within_vessel*blood_to_stationary)';

within_wall1=(radius>=R);
within_wall2=(radius<Rwv);
within_wall=bitand(within_wall1,within_wall2);

% Weighting of the influence from vessel wall scatterers

ampN2=amp.*(within_wall.*(sin(angleP).^2)*6)';

outside=(radius>=Rwv);  
ampN3=amp.*(outside)';

ampNow=ampN1+ampN2+ampN3;

% Generate the rotated and offset block of sample

    theta=45/180*pi;
    xnew=x*cos(theta)+zP*sin(theta);
    znew=zP*cos(theta)-x*sin(theta)+z_depth;
    znew=znew-(movResp(m)*znew/0.032);

% Save the matrix with the values

   positions=[xnew; yP; znew;]';

% Including an "offset" scatterer that will make the RF lines have the
% same start time, and also a stop scatterer.

   offset1=[0 0 0.002]; 
   offset2=[0 0 0.058]; 

   positions=[offset1
              positions
        offset2];

   ampNow=[0
           ampNow
     0];

   filename=['Position/pos_simMW' num2str(m)];
   save(filename,'positions','ampNow');
   clear positions

%  Propagate the scatterers and aliaze them
%  to lie within the correct range

    x1=x;
    x=x+velocity*Tprf;
    outside_range=(x>x_range/2);
    x=x-x_range*outside_range;

 end

Answer 1

[Stephen23]

When I run your code the value of N is

>> N
N =     15593.9233856041

clearly this is not an integer, so it cannot be used as an input for a rand call.

[Yapo OBOUE]

Hi dear Stephen, is there a function that can I use instead of rand to solve this problem.

[Stephen23]

".. is there a function that can I use instead of rand to solve this problem. "

What exactly is the problem?