Question

如果我有一个由数字编号组成的数组，请说

A = [1.3, 2.2, 2.3,4.2, 5.1, 3.2, 5.3, 3.3, 2.1,1.1, 5.2, 3.1]

我想提取只有整数在数组中的数字，然后是.1，.2和.3。例如，我不想在我的新阵列中包含1，因为A中不存在1.2。我想包括5，因为5.1,5.2和5.3都在A中。我怎么能这样做？接受MatLab或Python答案！

编辑** 谢谢。我现在意识到，我可能会问错误的问题，而不是打印带小数的整数.1，.2，.3我希望最后一个数组由A的浮点数组成，但只有两个都有的浮点数.1，.2，.3落后于同一个整数。遗憾！

Answer 1

在 Python 中，您可以执行以下操作：

import operator

A = [1.3, 2.2, 2.3,4.2, 5.1, 3.2, 5.3, 3.3, 2.1,1.1, 5.2, 3.1]

s = set(int(str(i).split('.')[0]) for i in A)

res = []
for n in s:
    if all(x in A for x in map(operator.add, [n, n, n], [0.1, 0.2, 0.3])):
        res.append(n)

<强>输出：

>>> res
[2, 3, 5]

修改

如果你想要的是获得在同一整数后面有.1，.2和.3的浮点数，请尝试以下方法：

for n in s: temp = map(operator.add, [n, n, n], [0.1, 0.2, 0.3]) if all(x in A for x in temp): res.extend(temp)

<强>输出：

>>> res [2.1, 2.2, 2.3, 3.1, 3.2, 3.3, 5.1, 5.2, 5.3]

Answer 2

使用 Python ，您可以：

import numpy as np
A = [1.3, 2.2, 2.3, 4.2, 5.1, 3.2, 5.3, 3.3, 2.1, 1.1, 5.2, 3.1]
b = set([int(i) for i in A if np.all([j in A for j in (np.array([1, 2, 3]) + 10*int(np.floor(i)))/10.0])])

其中b是

set([2, 3, 5])

（可以使用list轻松转换为列表。）

<强>评论：

我乘以10并除以10.0以避免浮点运算问题。在问题中不清楚您是否希望比较是基于数字或字符串。

Answer 3

使用Python，您可以使用itertools.groupby按浮动的值对其进行分组，并检查小数是否是[1,2,3]的超集：

from itertools import groupby
needed_decimals = set([1, 2, 3])

a = [1.3, 2.2, 2.3,4.2, 5.1, 3.2, 5.3, 3.3, 2.1,1.1, 5.2, 3.1]

pairs = [tuple(int(y) for y in str(x).split('.')) for x in sorted(a)]
#=> [(1, 1), (1, 3), (2, 1), (2, 2), (2, 3), (3, 1), (3, 2), (3, 3), (4, 2), (5, 1), (5, 2), (5, 3)]
integers = [integer for integer, numbers in groupby(pairs, lambda x: x[0]) if set(x[1] for x in numbers) >= needed_decimals]
#=> [2,3,5]

Answer 4

在 MATLAB 中（可能不是最好的算法）：

clc; clear;

tolerance = 10^(-15);
% Tolerance is useful in order to compare arrays, because the "==" operator
% can lean to wrong results.

% The fractional parts we are interested in.
desirable_list = [0.1 0.2 0.3];

% Because we are going to work with ordered lists, we order the
% desirable_list as well.
desirable = sort(desirable_list, 'ascend');

% Our list and the sorted list.
A = [1.3, 2.2, 2.3, 4.2, 5.1, 3.2, 5.3, 3.3, 2.1, 1.1, 5.2, 3.1];
A_sorted = sort(A);

% Getting the integer parts (uniquely) of our list.
integer_parts = unique(fix(A));

% Getting the elements that satisfy our criteria in an ordered list in an
% array called S.
S = [];
for j = integer_parts
    m1 = (A_sorted(fix(A_sorted) == j));
    if m1 < 0
        m1 = sort(m1, 'descend');
    end


    if length(m1) == length(desirable) & abs(abs(m1) - desirable) < abs(j) + tolerance
        S = [S m1];
    end
end

% Getting the elements we are interested in, in the specific order they
% appear in our original list.

V = zeros(1,length(S));
l = 1;
for k = 1:length(A)
    if ismember(A(k), S)
        V(l)= A(k);
        l = l + 1;
    end
end
A
V

<强>输出：

A =

    1.3000    2.2000    2.3000    4.2000    5.1000    3.2000    5.3000    3.3000    2.1000    1.1000    5.2000    3.1000


V =

    2.2000    2.3000    5.1000    3.2000    5.3000    3.3000    2.1000    5.2000    3.1000

>>

Answer 5

MATLAB解决方案:(由于问题中的更新而更新）

A = [1.3, 2.2, 2.3,4.2, 5.1, 3.2, 5.3, 3.3, 2.1,1.1, 5.2, 3.1]
INC = [.1 .2 .3];
F = floor(A);
U = unique(F,'stable');
%find unique  values of F
B = bsxfun(@plus,U,INC.');
%with broadcasting sum each element with [.1 .2 .3]
%in MATLAB R2016b you can write B = U + INC.';
IDX = all(ismember(B,A));
%for each integer I if  I+[.1 .2 .3] exist in the array return index of it
OUT =B(:,IDX);
%extract output

更紧凑的形式：

B = bsxfun(@plus,unique(floor(A),'stable'),INC.');
OUT = B(:,all(ismember(B,A)))

在MATLAB R2016b或Octave中可以写成：

B = unique(floor(A),'stable') + INC.';
OUT = B(:, all(ismember(B,A)))

结果

OUT =

   2.1000   3.1000   5.1000
   2.2000   3.2000   5.2000
   2.3000   3.3000   5.3000

Answer 6

set（[x for map in map（int，l）if if all [[float（str（x）+'。'+ str（e））in l for e in [1,2,3 ]]）]）

在一行中诀窍

如何从数组中删除不符合条件的某些值？

6 个答案: