truncate at 10^-3

i have this code i want to truncate the solution at 10^-3 at each iteraion can anyone help me

t0=0;
y0=1;
tn=1;
h=0.1;
t=[t0:h:tn];
f=@(t,y)(1+t-y)

f = function_handle with value:
    @(t,y)(1+t-y)

f1=@(t,y)1

f1 = function_handle with value:
    @(t,y)1

f2=@(t,y)-1

f2 = function_handle with value:
    @(t,y)-1

n=length(t);
y_t=zeros(1,n);
y_t(1)=y0;
for i=1:n-1
    y_t(i+1)=y_t(i)+h*f(t(i),y_t(i))+(h^2/2)*(f1(t(i),y_t(i))+f2(t(i),y_t(i))*f(t(i),y_t(i)));
end

Answer 1

[Matt J]

A few options:

x=round(pi,3)

x = 3.1420

y=floor(pi*1000)/1000

y = 3.1410

sprintf('%.3f',x)

ans = '3.142'

sprintf('%.3f',y)

ans = '3.141'

[diadalina]

i'm trying this but it doesn't work i want 3 decimals

[Matt J]

You shouldn't be getting anything non-zero after the 3rd decimal, or printing anything after the 3rd decimal if using sprintf.

[diadalina]

i'm trying fo truncate at 10^3 y-tt is the trancted vector y-t is the vector without truncation but they are different i can't find where the problem

n=length(t);
y_tt=zeros(1,n);
y_tt(1)=fix(y0*10^3)/10^3;
for i=1:n-1
    %y_tt(i)=fix(y_tt(i)*10^3)/10^3;
    y_tt(i+1)=y_tt(i)+h*f(t(i),y_tt(i))+(fix(h^2/2*10^3)/10^3)*(f1(t(i),y_tt(i))+f2(t(i),y_tt(i))*f(t(i),y_tt(i)));
    y_tt(i)=fix(y_tt(i+1)*10^3)/10^3;
end
y_t=zeros(1,n);
y_t(1)=y0;
for i=1:n-1
    y_t(i+1)=y_t(i)+h*f(t(i),y_t(i))+h^2/2*(f1(t(i),y_t(i))+f2(t(i),y_t(i))*f(t(i),y_t(i)))
end
M=[y_tt',y_t']

this what matlab gives to me they are differents :

M =

1.004 1

1.019 1.005

1.041 1.019

1.07 1.0412

1.107 1.0708

1.149 1.1071

1.197 1.1494

1.249 1.1972

1.307 1.25

1.368 1.3072

1.3685 1.3685

can you help me please , i shoud find the same 3 firsts dicimals in y_tt and y_t

[Matt J]

I imagine you would want to do this:

y_t(1)=y0;
for i=1:n-1
    y_t(i+1)=y_t(i)+h*f(t(i),y_t(i))+h^2/2*(f1(t(i),y_t(i))+f2(t(i),y_t(i))*f(t(i),y_t(i)))
end

y_tt=fix(y_t*1e3)/1e3;

M=[y_tt',y_t']