# How to extract a specific value from a loop.

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Westin Messer on 31 Aug 2018
Commented: Dennis on 3 Sep 2018
Hello
I wrote this code to model a simple projectile motion problem. What I would like to do now is output the value for x after 2 seconds but I don't know how to pull just one value out of a for loop.
%Projectile motion
v0= 10;
a= 45;
h= .04;
a=a*pi/180;
g=9.8; %acceleration due to gravity in m/s^2
xmax=v0^2*sin(2*a)/g;
ymax=v0^2*sin(a)^2/(2*g);
td=2*v0*sin(a)/g; %total time
x1=0;
y1=0;
figure('color','white');
for t=0:h:td+h
plot(x1,y1,'bo')
hold all
xlim([0 1.1*xmax]);
ylim([0 1.1*ymax]);
title('Projectile Motion');
xlabel('Distance in meter');
ylabel('Height in meter');
getframe;
x1=x1+h*v0*cos(a); %Euler's method for x
y1=y1+h*(v0*sin(a)-g*t);%Euler's method for y
% x1(2) % this is where I'm having the problem
end

M on 31 Aug 2018
t is your time variable, so you have to use it to test if it's equal to 2seconds.
if t==2 % assumes your time units is seconds
x_2sec=x1;
end
but in your code, t will never reach 2 seconds.
Dennis on 3 Sep 2018
To check if t==1.32 would not work either. Due to floating point limitations t will not be exactly 1.32.

### More Answers (1)

GK on 31 Aug 2018
Yes you can. 1. If you remove semicolon at the end of expression, MATLAB simply shows it at the command line 2. Alternately, you can also print it in excel file using- xlswrite('x1values.xlsx', x1);