pivot | 易学教程

pandas: unstack rows into new columns

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问题 i have a df that looks like this: a date c 0 ABC 2020-06-01 0.1 1 ABC 2020-05-01 0.2 2 DEF 2020-07-01 0.3 3 DEF 2020-01-01 0.4 4 DEF 2020-02-01 0.5 5 DEF 2020-07-01 0.6 i would like to "unstack" column 'a' so my new df looks like this a date1 c1 date2 c2 date3 c3 date4 c4 0 ABC 2020-06-01 0.1 2020-05-01 0.2 nan nan nan nan 1 DEF 2020-07-01 0.3 2020-01-01 0.4 2020-02-01 0.5 2020-07-01 0.6 how can i do this? 回答1: Use GroupBy.cumcount for helper counter for MultiIndex and reshape by DataFrame

ACCESS/SQL Combining multiple rows with one column into one row and creating multiple columns

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问题 I've looked at quite a few examples and nothing fits quite like I need it to. I have a table that has item numbers in one column and image links in another column. The issue I have is I need to combine rows that have the same item number but need to move the data in the HTML_LINK column to multiple columns called imagelink1, imagelink2, imagelink3. The max amount of imagelink columns I will need is 5. I tried a pivot table which worked to combine the rows, but it creates a column the name of

ACCESS/SQL Combining multiple rows with one column into one row and creating multiple columns

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一看就懂的快速排序

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概念快速排序属于交换排序，主要步骤是使用基准元素进行比较，把小于基准元素的移动到一边，大于基准元素的移动到另一边。从而把数组分成两部分，然后再从这两部分中选取出基准元素，重复上面的步骤。过程如下：紫色：基准元素绿色：大于基准元素黄色：小于基准元素这种思路叫做分治法。基准元素基准元素的选取可随机选取。下面使用中我会使用第一位的元素作为基准元素。排序过程排序拆分过程如下图：紫色为基准元素，（每一轮都重新选取）绿色为其他元素第一轮第二轮第三轮如上图所示：若元素个数为n，因为排序过程中需要和全部元素都比较一遍，所以时间复杂度为O(n)，而平均情况下排序轮次需要logn轮，因此快速排序的平均时间复杂度为O(nlogn)。排序的实现方法实现方法有双边循环法和单边循环法双边循环法首选选取基准元素(pivot)4，并设置指针left和right，指向数组最左和最右两个元素，如下：第一次循环，先从right指针指向的数据(rightData)开始和基准元素比较若 rightData >= pivot，则right指针向左移动，若 rightData < pivot，则right指针不移动，切换到left指针 left指针指向数据(leftData)与基准元素比较，若 leftData <= pivot，则left指针向右移动，若 leftData >

一看就懂的快速排序

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概念快速排序属于交换排序，主要步骤是使用基准元素进行比较，把小于基准元素的移动到一边，大于基准元素的移动到另一边。从而把数组分成两部分，然后再从这两部分中选取出基准元素，重复上面的步骤。过程如下：紫色：基准元素绿色：大于基准元素黄色：小于基准元素这种思路叫做分治法。基准元素基准元素的选取可随机选取。下面使用中我会使用第一位的元素作为基准元素。排序过程排序拆分过程如下图：紫色为基准元素，（每一轮都重新选取）绿色为其他元素第一轮第二轮第三轮如上图所示：若元素个数为n，因为排序过程中需要和全部元素都比较一遍，所以时间复杂度为O(n)，而平均情况下排序轮次需要logn轮，因此快速排序的平均时间复杂度为O(nlogn)。排序的实现方法实现方法有双边循环法和单边循环法双边循环法首选选取基准元素(pivot)4，并设置指针left和right，指向数组最左和最右两个元素，如下：第一次循环，先从right指针指向的数据(rightData)开始和基准元素比较若 rightData >= pivot，则right指针向左移动，若 rightData < pivot，则right指针不移动，切换到left指针 left指针指向数据(leftData)与基准元素比较，若 leftData < pivot，则left指针向右移动，若 leftData >

Joining multiple rows into a single row without aggregation [Oracle]

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问题 I have the following query: select type, date, amount from table; And it gives the following result: TYPE DATE AMOUNT -------------------------------- A 30.6.2019 15 B 30.11.2019 20 C 22.12.2019 17 What I want to do is write a query that would return the following: TYPE1 DATE1 AMOUNT1 TYPE2 DATE2 AMOUNT2 TYPE3 DATE3 AMOUNT3 ------------------------------------------------------------------------------------------------------ A 30.6.2019 15 B 30.11.2019 20 C 22.12.2019 17 The number of rows

Joining multiple rows into a single row without aggregation [Oracle]

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Hive: Is there a way to get the aggregates of all the numeric columns existing in a table?

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问题 I have a table containing over 50 columns (both numeric and char), is there a way to get the overall statistics without specifying each column? As an example: a b c d 1 2 3 4 5 6 7 8 9 10 11 12 Ideally I would have something like: column_name min avg max sum a 1 5 9 15 b 2 6 10 18 c 3 7 11 21 d 4 8 12 24 Nevertheless, getting one aggregate at a time it would be more more than helpful. Any help/idea would be highly appreciated. Thank you, O 回答1: You can parse DESCRIBE TABLE output using AWK

Pivoting to append the last 6 payments for 24 loans

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问题 I am building a query in Microsoft sql server where I want to find the active loans as well as some information on them. I have built out a common table expression that gives me the correct population. Now I need to get the last 6 payments starting from today. I have a another common table expression that gives all the payments and the payment data received but I am not sure how to pivot and append the last 6 payments such that I have something like this: This is what the query and output

Filtering table to create another table in Excel

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问题 I need to receive values from a table where a condition is met. For example I have names and I need to take all values from a table where the name appears. For example the table consists of date, name, expenditures: Date Name Expenditures 2019-01-28 Sara 2.45 2019-04-26 John 32.67 2019-05-07 Peter 55.88 2019-06-14 Sara 62.09 2019-07-03 Sara 12.94 2019-09-30 Peter 5.64 I need to receive all expenditures which has been made by Sara and the Date days when it was done. The result should be the

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