How to stop rounding values when i use array?
134 views (last 30 days)
Show older comments
Hello everyone,
clear; clc;
syms f(y,t); %sym func
h = 0.1; %step size
ti = 0; %initial value
yi = 1; %value at ti = 0
f(t,y) = (1+2*t)*sqrt(y); %dif equation
for ti=[0:h:0.9] % t[0,1] condition with step size
k1 = f(ti,yi); %formula
k2 = vpa(f(ti+((1/2)*h),yi+((1/2)*k1*h))); %formula
k3 = vpa(f(ti+((1/2)*h),yi+((1/2)*k2*h))); %formula
k4 = vpa(f(ti+h,yi+k3*h)); %formula
c = ti+h; %trying to make it equal to another step
c = yi + ((1/6)*(k1 + 2*k2 + 2*k3 +k4)*h); %formula
ti = ti+h; % for calculating one step forward
yi = c %my values
end
This is my code. When i run this code i get these values which is alright for me.
yi = 1.113024864238065836914069386071
yi = 1.2543996857913360546038612123358
yi = 1.4280244537263716534345718377563
yi = 1.6383991563454554525623395070174
yi = 1.8906237821755359512988676861658
yi = 2.1903983207422986759010819641543
yi = 2.5440227630548922996833947540414
yi = 2.9583971018166219626153507261848
yi = 3.4410213314236507023824643153582
yi = 3.9999954478254578455556866889108
But when i use an array to plot these values. It automatically rounds them to closest value which is not alright for me cuz i need to plot the error as well. How can i solve this
Code with array:
clear; clc;
syms f(y,t); %sym func
h = 0.1; %step size
ti = 0; %initial value
yi = 1; %value at ti = 0
f(t,y) = (1+2*t)*sqrt(y); %dif equation
a = [];
b = 1;
for ti=[0:h:0.9] % t[0,1] condition with step size
k1 = f(ti,yi); %formula
k2 = vpa(f(ti+((1/2)*h),yi+((1/2)*k1*h))); %formula
k3 = vpa(f(ti+((1/2)*h),yi+((1/2)*k2*h))); %formula
k4 = vpa(f(ti+h,yi+k3*h)); %formula
c = ti+h; %trying to make it equal to another step
c = yi + ((1/6)*(k1 + 2*k2 + 2*k3 +k4)*h); %formula
ti = ti+h; % for calculating one step forward
yi = c %my values
a(b)=c
b = b+1;
end
plot(a,"r*")
a = 1.1130 1.2544 1.4280 1.6384 1.8906 2.1904 2.5440 2.9584 3.4410 4.0000
i know it is not a big problem one of them is 3.99999 other one is 4.0000 but i would like to know how to solve this.
0 Comments
Accepted Answer
Cris LaPierre
on 7 Apr 2021
By default, MATLAB only displays 4 decimal places. This does not change the actual value. It's just for display. You can modify the display format using the format function.
a = 1.113024864238066
format long
a
More Answers (2)
David Hill
on 7 Apr 2021
The values in your array (a) are not rounded, they are only rounded in the display of them. To see the actual values, change format to long.
display(a);
format long;
display(a);
See Also
Categories
Find more on Number Theory in Help Center and File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!