concatenation | 易学教程

reading sections from a large text file in python efficiently

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问题 I have a large text file containing several million lines of data. The very first column contains position coordinates. I need to create another file from this original data, but that only contains specified non-contiguous intervals based on the position coordinates. I have another file containing the coordinates for each interval. For instance, my original file is in a format similar to this: Position Data1 Data2 Data3 Data4 55 a b c d 63 a b c d 68 a b c d 73 a b c d 75 a b c d 82 a b c d

How to append column number in front of every element?

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Here is a simple data: a <- c( "a" ,"a") b <- c("b", "b") df <- data.frame(a, b) df[] <- paste0(1:2, unlist(df[,1:2])) a b 1 1a 1b 2 2a 2b The output I am looking for is: a b 1 1a 2b 2 1a 2b Any efficient way to do this? This works, but I am sure there is a much better way. Thanks! df2[] <- paste0(col, unlist(t(df2[,1:2]))) t(df2) Try this: df[] <- Map(paste0, seq_along(df), df) df ## a b ## 1 1a 2b ## 2 1a 2b 来源： https://stackoverflow.com/questions/52708734/how-to-append-column-number-in-front-of-every-element

Multi-Level MYSQL Query In One Select Statement

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问题 Pretty straightforward SQL question here - I have three levels of data spread out over three tables. Table 1- Listings , Table 2 - Interests , Table 3 - Messages Table 1 -> Table 2, and Table 2 -> Table 3 have a One-To-Many Relationship There will always be listings, but there may or may not be interests for each listing, and there may or may not be messages for each interest. What I want to do is select all the information in 1 Select Statement in order to avoid multiple database calls. I

How to get the formatted view of YQL as result?

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YQL gives out result only in tree view. Is there any way to get the result in Formatted view?? Use an XSLT stylesheet to create a formatted view. Here is an example for an RSS feed: <?xml version="1.0" encoding="utf-8"?> <xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"> <xsl:output method="XML" encoding="utf-8" doctype-public="-//W3C//DTD XHTML 1.0 Transitional//EN" doctype-system=http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd indent="yes"/> <xsl:template match='//channel'> <page> <content> <module> <header layout="simple"> <layout-items> <block class=

Oracle : String Concatenation is too long

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问题 I have below SQL as a part of a view. In one of the schema I am getting " String Concatenation is too long " error and not able to execute the view. Hence I tried the TO_CLOB() and now VIEW is not throwing ERROR, but it not returning the result as well it keep on running.. Please suggest.... Sql: SELECT Iav.Item_Id Attr_Item_Id, LISTAGG(La.Attribute_Name ||'|~|' || Lav.Attribute_Value ||' ' || Lau.Attribute_Uom, '}~}') WITHIN GROUP ( ORDER BY ICA.DISP_SEQ,LA.ATTRIBUTE_NAME) AS ATTR FROM Item

PHP - Concatenating two variables

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问题 I'm a newbie stumped on the following. If I'm including an external file on a page that contains the following variable: $blurb_78 = "Lorem ipsum dolor."; How can I echo $blurb_78 on the local page? (where the 78 part is a generated article ID set to a variable labeled, $id ) The following doesn't work: echo $blurb_.$id; Thanks much for your help. 回答1: I think you mean a variable variable name like it is mentioned at the Variable variables page on the PHP site. In your case this should work

count lines with same value in column in python

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问题 I'm trying to reproduce the R aggregate() function in python but without concatenating. For each line, I just want to count the number of occurrences of lines with a similar value in a given column. I'm trying to work it out from a piece of code taken here: http://timotheepoisot.fr/2011/12/01/the-aggregate-function-in-python/ The modifications I implemented are indicated by ### . The problem I am currently having is that the first column [0] contains character strings and the code seems to

How to train mix of image and data in CNN using ImageAugmentation in TFlearn

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问题 I would like to train a convolutional neural network in Tflearn-Tensorflow using a mix of images (pixel info) and data. Because I have a short number of images, I need to use the Image Augmentation to increase the number of image samples that I pass to the network. But that means that I can only pass image data as input data, having to add the non-image data at a later stage, presumably before the fully connected layer. I can't work out how to do this, since it seems that I can only tell the

Referring to objects using variable strings in R

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问题 Edit: Thanks to those who have responded so far; I'm very much a beginner in R and have just taken on a large project for my MSc dissertation so am a bit overwhelmed with the initial processing. The data I'm using is as follows (from WMO publically available rainfall data): 120 6272100 KHARTOUM 15.60 32.55 382 1899 1989 0.0 1899 0.03 0.03 0.03 0.03 0.03 1.03 13.03 12.03 9999 6.03 0.03 0.03 1900 0.03 0.03 0.03 0.03 0.03 23.03 80.03 47.03 23.03 8.03 0.03 0.03 1901 0.03 0.03 0.03 0.03 0.03 17.03

Concatenating a string using Win32 API

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问题 What's the best way to concatenate a string using Win32? If Understand correctly, the normal C approach would be to use strcat , but since Win32 now deals with Unicode strings (aka LPWSTR ), I can't think of a way for strcat to work with this. Is there a function for this, or should I just write my own? 回答1: lstrcat comes in ANSI and Unicode variants. Actually lstrcat is simply a macro defined as either lstrcatA or lstrcatW . These functions are available by importing kernel32.dll . Useful if