Help with code: Matlab code not printing last verification line.

1 次查看（过去 30 天）
Tyw7
Tyw7 2015-10-12
评论： Geoff Hayes 2015-10-12
I can't get Matlab to print the last "data within tolerance" line:
function [integral] = intmidpoint(N)
clear
clc
%INTMIDPOINT numerical integration using the composite midpoint rule
clc
%define the integration limits
a=0;
b=2;
%this is the aim of absolute error required
aim = 0.001;
%define the number of sub-intervals to be used
if nargin == 1
n=N;
else
n=1;
end
h=(b-a)/n;
%approximate integral using the composite mid-point rule
integral=0.0;
%add the contribution of each sub-interval in turn
abs_err = realmax;
while abs_err>aim;
h=(b-a)/n;
integral=0.0;
for i=1:n;
x_left = a+(i-1)*h;
x_right = a+i*h;
x_half = (x_left+x_right)/2.0;
f_half = f(x_half);
integral = integral+h*f_half;
abs_err=abs(4-integral);
end;
fprintf('2 Midpoint approximation to integral using %g subintervals is %g. \n Data outside of tolerance. Abosolute error is %g, which is greater than 0.001. Increase the number of steps. \n',n,integral,abs_err);
n = n + 1;
if abs_err>aim;
continue;
fprintf('test Midpoint approximation to integral using %g subintervals is %g. \n Data within tolerance. Absolute error is %g, which is less than 0.001. \n',n,integral,abs_err);
end;
end;
end
%subfunction defines the integrand
function [f_value] = f(x)
f_value = (x)^3;
end

请先登录，再回答此问题。

回答（1 个）

Walter Roberson
Walter Roberson 2015-10-12
The "continue" is going to be executed before the fprintf() that is in the same "if"
  4 个评论
显示 2更早的评论
Geoff Hayes
Geoff Hayes 2015-10-12
Try this
if abs_err>aim
fprintf('test Midpoint approximation to integral using %g subintervals is %g. \n Data within tolerance. Absolute error is %g, which is less than 0.001. \n',n,integral,abs_err);
break;
end
Note that the
ans =
3.9990
is the output parameter returned from your function call. You are probably calling your function from the command line without assigning the output to a variable. Try calling your function as
[estIntegral] = intmidpoint(42);
to suppress the extra output. (Note that it is the use of the semi-colon that is suppressing the output.)

请先登录，再进行评论。

类别

在 Help Center 和 File Exchange 中查找有关 Matrix Indexing 的更多信息

标签

产品

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by