Save loop values in a matrix

How can i save the data of "Long" and "Lat" as a matrix?

clc

clear

format long g

% PROBLEM = GroundTrack Always same

ge = 398600.8; % Earth gravitational constant

% ge = 6.67191*(10^-11) ;

TWOPI = 2*pi;

MINUTES_PER_DAY = 1440.;

MINUTES_PER_DAY_SQUARED = (MINUTES_PER_DAY * MINUTES_PER_DAY);

MINUTES_PER_DAY_CUBED = (MINUTES_PER_DAY * MINUTES_PER_DAY_SQUARED);

fname = 'tle.txt';

fid = fopen(fname, 'r');

while (1)

% read first line

tline = fgetl(fid);

if ~ischar(tline)

break

end

Cnum = tline(3:7); % Catalog Number (NORAD)

SC = tline(8); % Security Classification

ID = tline(10:17); % Identification Number

epoch = str2double(tline(19:32)); % Epoch

TD1 = str2double(tline(34:43)); % first time derivative

TD2 = str2double(tline(45:50)); % 2nd Time Derivative

ExTD2 = tline(51:52); % Exponent of 2nd Time Derivative

BStar = str2double(tline(54:59)); % Bstar/drag Term

ExBStar = str2double(tline(60:61)); % Exponent of Bstar/drag Term

BStar = BStar*1e-5*10^ExBStar;

Etype = tline(63); % Ephemeris Type

Enum = str2double(tline(65:end)); % Element Number

TLEYear = tline(19:20) ;

TLEEpochDate = str2double(tline(21:32));

% read second line

tline = fgetl(fid);

if ~ischar(tline)

break

end

i = str2double(tline(9:16)); % Orbit Inclination (degrees)

raan = str2double(tline(18:25)); % Right Ascension of Ascending Node (degrees)

e = str2double(strcat('0.',tline(27:33))); % Eccentricity

omega = str2double(tline(35:42)); % Argument of Perigee (degrees)

M = str2double(tline(44:51)); % Mean Anomaly (degrees)

no = str2double(tline(53:63)); % Mean Motion

a = ( ge/(no*2*pi/86400)^2 )^(1/3); % semi major axis (m)

rNo = str2double(tline(64:68)); % Revolution Number at Epoch

end

fclose(fid);

satdata.epoch = epoch;

satdata.norad_number = Cnum;

satdata.bulletin_number = ID;

satdata.classification = SC; % almost always 'U'

satdata.revolution_number = rNo;

satdata.ephemeris_type = Etype;

satdata.xmo = M * (pi/180);

satdata.xnodeo = raan * (pi/180);

satdata.omegao = omega * (pi/180);

satdata.xincl = i * (pi/180);

satdata.eo = e;

satdata.xno = no * TWOPI / MINUTES_PER_DAY;

satdata.xndt2o = TD1 * 1e-8 * TWOPI / MINUTES_PER_DAY_SQUARED;

satdata.xndd6o = TD2 * TWOPI / MINUTES_PER_DAY_CUBED;

satdata.bstar = BStar;

GMTDelay = 0 ;

ERS = 360/(24*3600) ; % Earth Rotation Speed in deg/s

mapll = load('coast') ;

mlat = mapll.lat ;

mlong = mapll.long ;

plot (mlong,mlat,'b')

% xlim([-180 180])

% ylim([-90 90])

%

hold on

rgb = imread('Earthmap.jpg'); % read world equidistant projection image

map_image=image(-180:180,90:-1:-90,rgb); %

hold on

day_night_terminator=area(1,1,1,'FaceColor',[0.0,0.0,0.0],'FaceAlpha',0.5,'EdgeColor','None');

tnow = datetime('now') ;

[baseline,coords] = plotdaynightterminator(tnow-(GMTDelay/24)) ;

set(day_night_terminator,'BaseValue',baseline,'XData',coords(:,1),'YData',coords(:,2));

clear mapll ;

rad = 57.2957795130823 ;

% tnow = datetime('now') ;

FirstYear = ['1-Jan-20' TLEYear ' 00:00:00'];

EDay = days(tnow - FirstYear) ;

DeltaDay = (EDay - TLEEpochDate) ;

DeltaMinute = DeltaDay * 24 * 60 ;

step = 30 ; % in second

InitStart = 1 ;

Long=zeros(2,1);

Lat=zeros(2,1);

while (InitStart ~= 0 )

[pos, vel] = sgp4(DeltaMinute, satdata);

[Lat,Long,Alt] = ecef2lla(pos(1)*1000,pos(2)*1000,pos(3)*1000) ;

Lat(InitStart) = Lat*rad;

Long(InitStart) = (Long*rad) - 180 ;

Long = Long - (DeltaMinute*60*ERS) ;

if Long < -180

Long = Long + 360 ;

end

if Long > 180

Long = Long - 360 ;

end

Alt = Alt/1000 ; % convert m to km

DeltaMinute = DeltaMinute + (step/60) ;

hold on

h1 = plot(Long,Lat, 'or','MarkerFaceColor','r');

axis equal

drawnow

title([datestr(tnow) ' - [Time step : ' num2str(step) ' sec]'],'Fontsize', 14);

tnow = tnow+(step/(3600*24)) ;

%pause(0.5)

%xlim([-180 180])

%ylim([-90 90])

%set(h1,'Visible','off')

%InitStart = 0;

end

Answer 1

[KALYAN ACHARJYA]

If the resultant long and Lat are just numeric number use array to save the data

Example

iter=1;
Long=[];
Lat=[];
while condition
Long(iter)=
Lat(iter)=
iter=iter+1;
end 

If the resultant long and Lat are another vector (array/matrix) use cell array to save the data

iter=1;
Long={};
Lat={};
while condition
Long{iter}=
Lat{iter}=
iter=iter+1;
end 

If you are using for loop, then preallocation possible with exact array length. I see the while loop at the later section of the code, hence given the example using while loop. Still issue, please restructure the question withsimple example.

[Oscar Lionel]

The updated value keeps shifting on to and other cells remain 0.

How can i fix this?

[KALYAN ACHARJYA]

Use semicolon and off the display in command window till the iteration is complete. Do you know how many iterations going to iterate, then use for loop and assigned appropriate preallocation.

iter=1;
Long={};
Lat={};
while condition
Long{iter}=   ;
Lat{iter}=    ;
iter=iter+1;
end 
Long
Lat