Just create a `data.frame` with 0 length variables


eg

    nodata &lt;- data.frame(x= numeric(0), y= integer(0), z = character(0))
    str(nodata)
 
    ## &#39;data.frame&#39;:	0 obs. of  3 variables:
    ##  $ x: num 
    ##  $ y: int 
    ##  $ z: Factor w/ 0 levels: 
  
or to create a data.frame with 5 columns named a,b,c,d,e

    nodata &lt;- as.data.frame(setNames(replicate(5,numeric(0), simplify = F), letters[1:5]))


Perhaps:

    &gt; data.frame(aname=NA, bname=NA)[numeric(0), ]
    [1] aname bname
    &lt;0 rows&gt; (or 0-length row.names)



I have the following in Bash (In Linux)

    for dir in Movies/*
    do
      (cd &quot;$dir&quot; &amp;&amp; pwd|cut -d \/ -f5|tr -s &#39;\n&#39; &#39;, &#39; &gt;&gt; ../../movielist &amp;&amp;
      exiftool * -t -s3 -ImageSize -FileType|tr -s &#39;\t&#39; &#39;,&#39; &gt;&gt; ../../movielist )
    echo &quot;Movie $movies - $dir ADDED!&quot;
    let movies=movies+1
    done

But I wish to make it so the &quot;echo&quot; shows the following echo on the next line (Not concatenate with the last echo output but replace it) so to make it look like it is updating. Similar to how a progress bar with percent would show on the same line.




How to show and update echo on same line

I have a `users` table and a `payments` table, for each user, those of which have payments, may have multiple associated payments in the `payments` table. I would like to select all users who have payments, but only select their latest payment. I&#39;m trying this SQL but i&#39;ve never tried nested SQL statements before so I want to know what i&#39;m doing wrong. Appreciate the help

    SELECT u.* 
	FROM users AS u
		INNER JOIN (
			SELECT p.*
			FROM payments AS p
			ORDER BY date DESC
			LIMIT 1
        )
		ON p.user_id = u.id
	WHERE u.package = 1

MySQL INNER JOIN select only one row from second table

&gt; **Possible Duplicate:**  
&gt; [Create an Empty Data.Frame](https://stackoverflow.com/questions/10689055/create-an-empty-data-frame)  

&lt;!-- End of automatically inserted text --&gt;

I need to create an empty data frame in R with specified column names. Any simplest way ?





How to create empty data frame with column names specified in R?

> Possible Duplicate: 
> <a href="https://stackoverflow.com/questions/10689055/create-an-empty-data-frame" target="_blank" rel="noopener noreferrer">Create an Empty Data.Frame</a>

I need to create an empty data frame in R with specified column names. Any simplest way ?

I wonder, how can I create a numeric zero-length vector in R?

How to create a numeric vector of zero length in R

I would like to read a text file in R, line by line, using a for loop and with the length of the file. The problem is that it only prints character(0). This is the code:

    fileName=&quot;up_down.txt&quot;
    con=file(fileName,open=&quot;r&quot;)
    line=readLines(con) 
    long=length(line)
    for (i in 1:long){
	    linn=readLines(con,1)
	    print(linn)
    }
    close(con)




Read a text file in R line by line

Apparently, folk have figured out how to make [xkcd][1] style graphs [in Mathematica][2] and [in LaTeX][3]. Can we do it in R? Ggplot2-ers? A geom_xkcd and/or theme_xkcd?

I guess in base graphics, par(xkcd=TRUE)?  How do I do it?

![xkcd#1064][4]

As a first stab (and as much more elegantly shown below) in ggplot2, adding the jitter argument to a line makes for a great hand-drawn look.  So - 

    ggplot(mapping=aes(x=seq(1,10,.1), y=seq(1,10,.1))) + 
      geom_line(position=&quot;jitter&quot;, color=&quot;red&quot;, size=2) + theme_bw()

It makes for a nice example - but the axes and fonts appear trickier. Fonts appear solved (below), though. Is the only way to deal with axes to blank them out and draw them in by hand? Is there a more elegant solution? In particular, in ggplot2, can element_line in the new theme system be modified to take a jitter-like argument?

  [1]: http://xkcd.com/
  [2]: https://mathematica.stackexchange.com/questions/11350/xkcd-style-graphs
  [3]: https://tex.stackexchange.com/questions/74878/create-xkcd-style-diagram-in-tex
  [4]: http://i.stack.imgur.com/f2UqI.png
       &quot;FYI: I&amp;#39;ll be releasing a wolf into a randomly-chosen front yard sometime in the next 30 years. Now your fear is reasonable, and you don&amp;#39;t need to feel embarrassed anymore. Problem solved!&quot;


How can we make xkcd style graphs?

Yes I know why we always round to the nearest even number if we are in the exact middle (i.e. 2.5 becomes 2) of two numbers.  But when I want to evaluate data for some people they don&#39;t want this behaviour. What is the simplest method to get this:

    x &lt;- seq(0.5,9.5,by=1)
    round(x)

to be 1,2,3,...,10 and not 0,2,2,4,4,...,10.

Edit: To clearify: 1.4999 should be 1 after rounding. (I thought this would be obvious)

Round up from .5

In R, I&#39;d like to retrieve a list of global variables at the end of my script and iterate over them. Here is my code

    #declare a few sample variables
    a&lt;-10
    b&lt;-&quot;Hello world&quot;
    c&lt;-data.frame()
    
    #get all global variables in script and iterate over them
    myGlobals&lt;-objects()
    for(i in myGlobals){
      print(typeof(i))     #prints &#39;character&#39;
    }

My problem is that `typeof(i)` always returns `character` even though variable `a` and `c` are not character variables. How can I get the original type of variable inside the for loop?

Get type of all variables

I have a ``pandas dataframe`` in which one column of text strings contains comma-separated values. I want to split each CSV field and create a new row per entry (assume that CSV are clean and need only be split on &#39;,&#39;). For example, ``a`` should become ``b``:

    In [7]: a
    Out[7]: 
        var1  var2
    0  a,b,c     1
    1  d,e,f     2
    
    In [8]: b
    Out[8]: 
      var1  var2
    0    a     1
    1    b     1
    2    c     1
    3    d     2
    4    e     2
    5    f     2

So far, I have tried various simple functions, but the ``.apply`` method seems to only accept one row as return value when it is used on an axis, and I can&#39;t get ``.transform`` to work. Any suggestions would be much appreciated!

Example data: 

    from pandas import DataFrame
    import numpy as np
    a = DataFrame([{&#39;var1&#39;: &#39;a,b,c&#39;, &#39;var2&#39;: 1},
                   {&#39;var1&#39;: &#39;d,e,f&#39;, &#39;var2&#39;: 2}])
    b = DataFrame([{&#39;var1&#39;: &#39;a&#39;, &#39;var2&#39;: 1},
                   {&#39;var1&#39;: &#39;b&#39;, &#39;var2&#39;: 1},
                   {&#39;var1&#39;: &#39;c&#39;, &#39;var2&#39;: 1},
                   {&#39;var1&#39;: &#39;d&#39;, &#39;var2&#39;: 2},
                   {&#39;var1&#39;: &#39;e&#39;, &#39;var2&#39;: 2},
                   {&#39;var1&#39;: &#39;f&#39;, &#39;var2&#39;: 2}])

I know this won&#39;t work because we lose DataFrame meta-data by going through numpy, but it should give you a sense of what I tried to do: 

    def fun(row):
        letters = row[&#39;var1&#39;]
        letters = letters.split(&#39;,&#39;)
        out = np.array([row] * len(letters))
        out[&#39;var1&#39;] = letters
    a[&#39;idx&#39;] = range(a.shape[0])
    z = a.groupby(&#39;idx&#39;)
    z.transform(fun)

Split (explode) pandas dataframe string entry to separate rows

Let&#39;s say I have the following data frame:

    &gt; myvec
        name order_no
    1    Amy       12
    2   Jack       14
    3   Jack       16
    4   Dave       11
    5    Amy       12
    6   Jack       16
    7    Tom       19
    8  Larry       22
    9    Tom       19
    10  Dave       11
    11  Jack       17
    12   Tom       20
    13   Amy       23
    14  Jack       16

I want to count the number of distinct `order_no` values for each `name`. It should produce the following result:

    name	number_of_distinct_orders
    Amy 	2
    Jack	3
    Dave	1
    Tom 	2
    Larry	1

How can I do that?

Counting unique / distinct values by group in a data frame

&gt; **Possible Duplicate:**  
&gt; [Drop Columns R Data frame](https://stackoverflow.com/questions/4605206/drop-columns-r-data-frame)  

&lt;!-- End of automatically inserted text --&gt;

Let&#39;s say I have a dataframe with column c1, c2, c3.

I want to list just c1 and c2. How do I do that?

I&#39;ve tried:

    head(data[column!=&quot;c3&quot;])
    head(data)[,2]
    head(data[!&quot;c3&quot;])

List all column except for one in R

Working with a data frame similar to this:  

    set.seed(100)  
    df &lt;- data.frame(cat = c(rep(&quot;aaa&quot;, 5), rep(&quot;bbb&quot;, 5), rep(&quot;ccc&quot;, 5)), val = runif(15))             
    df &lt;- df[order(df$cat, df$val), ]  
    df  

       cat        val  
    1  aaa 0.05638315  
    2  aaa 0.25767250  
    3  aaa 0.30776611  
    4  aaa 0.46854928  
    5  aaa 0.55232243  
    6  bbb 0.17026205  
    7  bbb 0.37032054  
    8  bbb 0.48377074  
    9  bbb 0.54655860  
    10 bbb 0.81240262  
    11 ccc 0.28035384  
    12 ccc 0.39848790  
    13 ccc 0.62499648  
    14 ccc 0.76255108  
    15 ccc 0.88216552 

   
I am trying to add a column with numbering within each group. Doing it this way obviously isn&#39;t using the powers of R:  
  

     df$num &lt;- 1  
     for (i in 2:(length(df[,1]))) {  
       if (df[i,&quot;cat&quot;]==df[(i-1),&quot;cat&quot;]) {  
         df[i,&quot;num&quot;]&lt;-df[i-1,&quot;num&quot;]+1  
         }  
     }  
     df  

       cat        val num  
    1  aaa 0.05638315   1  
    2  aaa 0.25767250   2  
    3  aaa 0.30776611   3  
    4  aaa 0.46854928   4  
    5  aaa 0.55232243   5  
    6  bbb 0.17026205   1  
    7  bbb 0.37032054   2  
    8  bbb 0.48377074   3  
    9  bbb 0.54655860   4  
    10 bbb 0.81240262   5  
    11 ccc 0.28035384   1  
    12 ccc 0.39848790   2  
    13 ccc 0.62499648   3  
    14 ccc 0.76255108   4  
    15 ccc 0.88216552   5  

  
What would be a good way to do this?






Numbering rows within groups in a data frame

In R when you need to retrieve a column index based on the name of the column you could do

    idx &lt;- which(names(my_data)==my_colum_name)

Is there a way to do the same with pandas dataframes?

Content Type	Original Author	Original Content on Stackoverflow
Question	Surjya Narayana Padhi	View Question on Stackoverflow
Solution 1 - R	mnel	View Answer on Stackoverflow
Solution 2 - R	IRTFM	View Answer on Stackoverflow

How to create empty data frame with column names specified in R?

R Problem Overview

R Solutions

Solution 1 - R

Solution 2 - R

MySQL INNER JOIN select only one row from second table

How to show and update echo on same line

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