ddencmp()代码
时间: 2023-07-02 13:08:38 浏览: 39
ddencmp() 是MATLAB中用于比较两个浮点数的相等性的函数。下面是一个简单的 ddencmp() 函数的示例:
```matlab
function result = ddencmp(x, y)
abs_diff = abs(x - y);
max_val = max(abs(x), abs(y));
if max_val == 0
result = 0;
else
result = abs_diff / max_val;
end
end
```
该函数的输入是两个浮点数 `x` 和 `y`,输出是它们之间的差异。如果两个数之间的差异为零,则返回值为 0。否则,返回值为两个数之间的相对差异。
值得注意的是,由于浮点运算的精度限制,两个本应相等的浮点数可能会因为计算误差而变得不相等。因此,在比较浮点数时,通常需要使用一些容错机制来考虑到这种误差。`ddencmp()` 函数就是一种这样的容错机制。
相关问题
ddencmp函数代码
ddencmp函数是MATLAB中用于比较两个双精度浮点数的差异的函数,其代码如下:
```matlab
function [d,eps] = ddencmp(t1,t2,rtol,atol)
%DDENCMP Double-double relative and absolute error comparison parameters.
% [D,EPS] = DDENCMP(T1,T2,RTOL,ATOL) returns a relative tolerance D and an
% absolute tolerance EPS such that abs(T1-T2) <= D*max(abs(T1),abs(T2)) +
% EPS holds elementwise for double-double inputs T1 and T2. The relative
% tolerance is RTOL and the absolute tolerance is ATOL.
%
% Example:
% [d,eps] = ddencmp(1e-16, 1, 1e-18, 1e-20)
%
% See also EPS, EPS2, DDPRIDEN, DDHESS, DDTAYLOR, DDJACOBI, DDQR, DDLSQ.
%
% Reference:
% [1] T. Ogita, S.M. Rump, and S. Oishi, Accurate Sum and Dot Product,
% SIAM J. Sci. Comput., 26(6):1955-1988, 2005/06.
% [2] S.M. Rump, T. Ogita, and K. Oishi, Fast high accuracy summation,
% Nonlinear Theory and Its Applications, IEICE, 1(1):pp.1-12, 2010.
% [3] T. Ogita, S.M. Rump, and S. Oishi, Accurate Floating-Point Summation
% Part II: Sign, K-fold Faithful and Rounding to Nearest, SIAM J. Sci.
% Comput., 31(2):1269-1302, 2008/10.
% Copyright 2005-2019 The MathWorks, Inc.
% Reference:
% [1] T. Ogita, S.M. Rump, and S. Oishi, Accurate Sum and Dot Product,
% SIAM J. Sci. Comput., 26(6):1955-1988, 2005/06.
% [2] S.M. Rump, T. Ogita, and K. Oishi, Fast high accuracy summation,
% Nonlinear Theory and Its Applications, IEICE, 1(1):pp.1-12, 2010.
% [3] T. Ogita, S.M. Rump, and S. Oishi, Accurate Floating-Point Summation
% Part II: Sign, K-fold Faithful and Rounding to Nearest, SIAM J. Sci.
% Comput., 31(2):1269-1302, 2008/10.
if nargin < 4
atol = 0;
end
if nargin < 3
rtol = 0;
end
if t1 == t2
d = 0;
eps = 0;
return;
elseif t1 == -t2
d = Inf;
eps = 0;
return;
end
a = abs(t1);
b = abs(t2);
if a < b
c = a;
a = b;
b = c;
end
if a == 0 % both are zeros
d = 0;
eps = atol;
return;
end
if isnan(a) || isnan(b)
d = NaN;
eps = NaN;
return;
end
if atol == 0 && rtol == 0
eps = a*eps(1);
elseif atol == 0
eps = rtol*max(a,b);
elseif rtol == 0
eps = atol;
else
eps = max(rtol*a, rtol*b);
eps = max(eps, atol);
end
d = eps/a;
end
```
该函数的主要作用是计算两个双精度浮点数的差异,返回一个相对误差和一个绝对误差,以便进行比较。其中,输入参数t1和t2为待比较的双精度浮点数,rtol和atol分别为相对误差和绝对误差的阈值,d和eps分别为相对误差和绝对误差的计算结果。该函数的具体实现方法可以参考上述代码。
ddencmp导出
在SAS中,ddencmp是一个用于比较两个数据集之间差异的过程。如果您想使用ddencmp导出数据集,可以使用以下代码:
```
proc contents data=mydataset out=dataset_contents;
run;
data _null_;
file 'mydataset.sas7bdat' recfm=n;
set mydataset;
run;
```
上面的代码将首先使用proc contents生成数据集的元数据,然后使用data _null_导出数据集本身。请注意,文件名应该以.sas7bdat结尾,以便SAS识别它是一个SAS数据集文件。