Why does inequality give different values even though its evaluating the exact same matrix ??

Question

HabenG 2021-12-11

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1608525-why-does-inequality-give-different-values-even-though-its-evaluating-the-exact-same-matrix

评论： Walter Roberson 2021-12-11

采纳的回答： Walter Roberson

td.mat

在 MATLAB Online 中打开

Howcome these two yield different values ??

load td
version1 = sort(td(td(:,5) < 11.29))
version1 = 8×1
   11.1700
   11.1750
   11.1750
   11.1901
   11.2000
   11.2200
   11.2848
   11.3312
t = (td(:,5));
version2 = sort(t(t < 11.29))
version2 = 8×1
   11.1700
   11.1750
   11.1750
   11.2000
   11.2200
   11.2486
   11.2800
   11.2848
version1 - version2
ans = 8×1
         0
         0
         0
   -0.0099
   -0.0200
   -0.0286
    0.0048
    0.0464

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Walter Roberson 2021-12-11

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1608525-why-does-inequality-give-different-values-even-though-its-evaluating-the-exact-same-matrix#answer_852690

在 MATLAB Online 中打开

sort(td(td(:,5) < 11.29))

td is a 2D array with multiple columns. You construct a mask from one of the columns, and you use it to index the entire td array -- which by linear indexing is going to effectively have it operate on the first column.

t = (td(:,5));
sort(t(t < 11.29))

but here you extract the column and your linear indexing is against the extracted version that only contains the one column.

2 个评论
显示无隐藏无

HabenG 2021-12-11

Thanks that explains it. I did that to avoid the binary out put from the inequality. what would be a good way to evalueate the inequality and get the actual values?