简答：浮动不精确问题

Question

我实际上在＆＃34; np.ceil＆＃34;中遇到了一些问题。在python中。

<?php

namespace App\Providers;

use App\Post;
use App\Tag;

use Illuminate\Support\Facades\View;
use Illuminate\Support\ServiceProvider;

class AppServiceProvider extends ServiceProvider
{

    protected $defer = true;

    /**
     * Bootstrap any application services.
     *
     * @return void
     */
    public function boot()
    {
        View::composer('layouts.sidebar', function ($view) {

            $view->with('archives', Post::archives());
            $view->with('tags', Tag::has('posts')->pluck('name'));

        });
    }

    /**
     * Register any application services.
     *
     * @return void
     */
    public function register()
    {
        //
    }
}

我应该得到类似的东西：

import numpy as np

x_start = 0
y_start = 0
x_end = 2
y_end = 1
x_step = 0.4
y_step = 0.3

x_segment = int(np.ceil((x_end-x_start)/x_step))
y_segment = int(np.ceil((y_end-y_start)/y_step))

print "N. x: " + str(x_segment)
print "N. y: " + str(y_segment)

matrix = np.zeros((y_segment, x_segment), dtype=int)

import matplotlib.pyplot as plt
import matplotlib.patches as patches

def frange(x, y, jump):
  while x < y:
    yield x
    x += jump
for y in frange(y_start, y_end, y_step):
    print "***"
    for x in frange(x_start, x_end, x_step):
        count = 0
        print "(" + str(x) + "; " + str(y) + ")   m[" + str(y_segment - int(np.ceil(y/y_step)) - 1) + "][" + str(int(np.ceil(x/x_step)))+"]" + " | x/x_step: " + str(x/x_step) + " | np.ceil(x/x_step): " + str(int(np.ceil(x/x_step)))

但数字＆＃34; 3＆＃34;被替换为＆＃34; 4＆＃34;。

...
***
(0; 0)   m[3][0] | x/x_step: 0.0 | np.ceil(x/x_step): 0
(0.4; 0)   m[3][1] | x/x_step: 1.0 | np.ceil(x/x_step): 1
(0.8; 0)   m[3][2] | x/x_step: 2.0 | np.ceil(x/x_step): 2
(1.2; 0)   m[3][3] | x/x_step: 3.0 | np.ceil(x/x_step): 3
(1.6; 0)   m[3][4] | x/x_step: 4.0 | np.ceil(x/x_step): 4
***
...

你知道为什么吗？我该如何修复我的代码？谢谢！

Answer 1

简答：浮动不精确问题

答案很长：

frange似乎有一些浮点精度问题。看看当你完成frange时会发生什么：

如果您只是打印原始花车：

>>> [x for x in frange(x_start, x_end, x_step)]
[0, 0.4, 0.8, 1.2000000000000002, 1.6]

出于某种原因，1.2并不完全是1.2。当你这样做时：

np.ceil(1.2000000000000002/x_step)

你得到4.0（换句话说，np.ceil可以正常工作）。

您想要的基本上是np.ceil(1.2/x_step)，等于3.0

我建议您在应用np.round()

之前使用x或类似内容来围绕np.ceil()值

python中的np.ceil不起作用

1 个答案:

简答：浮动不精确问题