Quoting directly from the help page for `factor`:

To transform a factor f to its original numeric values, `as.numeric(levels(f))[f]` is recommended and slightly more efficient than `as.numeric(as.character(f))`. 


You can combine the two functions; coerce to characters thence to numerics:

    &gt; fac &lt;- factor(c(&quot;1&quot;,&quot;2&quot;,&quot;1&quot;,&quot;2&quot;))
    &gt; as.numeric(as.character(fac))
    [1] 1 2 1 2



I&#39;m using [&quot;Closure Compiler&quot;][1], when compiling my scripts I spend the following:

Before compiling:

    // ==ClosureCompiler==
    // @compilation_level SIMPLE_OPTIMIZATIONS
    // @output_file_name default.js
    // @formatting pretty_print,print_input_delimiter
    // ==/ClosureCompiler==
    
    var myObj1 = (function() {
    
      var undefined;   //&lt;----- declare undefined
    
      this.test = function(value, arg1) {
    
        var exp = 0;
        arg1 = arg1 == undefined ? true : arg1;  //&lt;----- use declare undefined
        exp = (arg1) ? value * 5 :  value * 10;
    
        return exp;
      };
    
      return this;
    }).call({});
        
    var myObj2 = (function() {
    
      this.test = function(value, arg1) {

        var exp = 0;
        arg1 = arg1 == undefined ? true : arg1;  //&lt;----- without declare undefined
        exp = (arg1) ? value * 5 :  value * 10;
    
        return exp;
      };
    
      return this;
    }).call({});

Compiled:

    // Input 0
    var myObj1 = function() {
      this.test = function(b, a) {
        a = a == void 0 ? true : a;  //&lt;-----
        var c = 0;
        return c = a ? b * 5 : b * 10
      };
      return this
    }.call({}), myObj2 = function() {
      this.test = function(b, a) {
        a = a == undefined ? true : a; //&lt;-----
        var c = 0;
        return c = a ? b * 5 : b * 10
      };
      return this
    }.call({});

With this I believe the question of the use of &quot;void 0 &quot; and &quot;undefined&quot;, is there any difference in the use or the two cases are well?.

**Edit**

if I define &quot;var undefined&quot; compiled with &quot;void 0 &quot;, if I did not define &quot;undefined&quot; compiled with &quot;undedined. &quot; then not a matter of number of characters between &quot;undefined&quot; and &quot;void 0&quot;

[Test][2]

**Edit II: performance, based on [this link][3]**

[Code and Test][4]

**IE 8:**&lt;br /&gt;
  typeof: 228ms&lt;br /&gt;
  undefined: 62ms&lt;br /&gt;
  void 0: 57ms&lt;br /&gt;

**Firefox 3.6:**&lt;br /&gt;
  typeof: 10ms&lt;br /&gt;
  undefined: 3ms&lt;br /&gt;
  void 0: 3ms&lt;br /&gt;

**Opera 11:**&lt;br /&gt;
  typeof: 67ms&lt;br /&gt;
  undefined: 19ms&lt;br /&gt;
  void 0: 20ms&lt;br /&gt;

**Chrome 8:**&lt;br /&gt;
  typeof: 3ms&lt;br /&gt;
  undefined: 5ms&lt;br /&gt;
  void 0: 3ms&lt;br /&gt;


  [1]: http://closure-compiler.appspot.com/home
  [2]: http://jsfiddle.net/5m2DC/
  [3]: http://typeofnan.blogspot.com/2011/01/typeof-is-fast.html
  [4]: http://jsfiddle.net/mHx3T/3/

difference between &quot;void 0 &quot; and &quot;undefined&quot;

I&#39;m using psql to access a postgres database. When viewing the metadata of a table, is there any way to see whether an index of a table is a clustered index?

I heard that the PRIMARY KEY of a table is automatically associated with a clustered index, is it true?

About clustered index in postgres

I am manipulating a data frame using the reshape package. When using the melt function, it factorizes my value column, which is a problem because a subset of those values are integers that I want to be able to perform operations on.

Does anyone know of a way to coerce a factor into an integer? Using `as.character()` will convert it to the correct character, but then I cannot immediately perform an operation on it, and `as.integer()` or `as.numeric()` will convert it to the number that system is storing that factor as, which is not helpful.

Thank you!

Jeff

Convert factor to integer

I am manipulating a data frame using the reshape package. When using the melt function, it factorizes my value column, which is a problem because a subset of those values are integers that I want to be able to perform operations on.
Does anyone know of a way to coerce a factor into an integer? Using <code>as.character()</code> will convert it to the correct character, but then I cannot immediately perform an operation on it, and <code>as.integer()</code> or <code>as.numeric()</code> will convert it to the number that system is storing that factor as, which is not helpful.
Thank you!
Jeff

I have this file (http://b7hq6v.alterupload.com/en/) that I want to read in R with `read.csv`. But I am not able to detect the correct encoding. It seems to be a kind of UTF-8. I am using R 2.12.1 on an WindowsXP Machine. 
Any Help?

How to detect the right encoding for read.csv?

I know that this question might be a cliche, but I&#39;m having hard time doing it.

I&#39;ve data set in the following format:

&lt;pre&gt;
    Date            Visits
    
    11/1/2010       696537
    11/2/2010       718748
    11/3/2010       799355
    11/4/2010       805800
    11/5/2010       701262
    11/6/2010       531579
    11/7/2010       690068
    11/8/2010       756947
    11/9/2010       718757
    11/10/2010      701768
    11/11/2010      820113
    11/12/2010      645259
&lt;/pre&gt;

I want to create a time-series plot, with x-axis representing time &amp; y-axis vists. Also, I want to mark the x-axis with date. The code I was using is the following:

    dm$newday = as.POSIXct(strptime(dm$Day, format=&quot;%Y-%m-%d&quot;))
    plot(as.Date(dm$day),dm$visits)
    axis.Date(1,Day,at=seq(as.Date(&quot;2010/10/30&quot;), as.Date(&quot;2011/01/29&quot;),by=&quot;days&quot;))





Plotting time-series with Date labels on x-axis

I want to use ggplot to loop over several columns to create multiple plots, but using the placeholder in the for loop changes the behavior of ggplot.

If I have this:

    t &lt;- data.frame(w = c(1, 2, 3, 4), x = c(23,45,23, 34), 
    y = c(23,34,54, 23), z = c(23,12,54, 32))


This works fine:

    ggplot(data=t, aes(w, x)) + geom_line()

But this does not:

    i &lt;- &#39;x&#39;
    ggplot(data=t, aes(w, i)) + geom_line()

Which is a problem if I want to eventually loop over x, y and z. 
Any help?

Looping over variables in ggplot

I&#39;d like to remove the lines in this data frame that:

a) **contain `NA`s across all columns.** Below is my example data frame. 

                 gene hsap mmul mmus rnor cfam
    1 ENSG00000208234    0   NA   NA   NA   NA
    2 ENSG00000199674    0   2    2    2    2
    3 ENSG00000221622    0   NA   NA   NA   NA
    4 ENSG00000207604    0   NA   NA   1    2
    5 ENSG00000207431    0   NA   NA   NA   NA
    6 ENSG00000221312    0   1    2    3    2


Basically, I&#39;d like to get a data frame such as the following.

                 gene hsap mmul mmus rnor cfam
    2 ENSG00000199674    0   2    2    2    2
    6 ENSG00000221312    0   1    2    3    2

b) **contain `NA`s in only some columns**, so I can also get this result:

                 gene hsap mmul mmus rnor cfam
    2 ENSG00000199674    0   2    2    2    2
    4 ENSG00000207604    0   NA   NA   1    2
    6 ENSG00000221312    0   1    2    3    2



Remove rows with all or some NAs (missing values) in data.frame

Most of the questions about merging data.frame in lists on SO don&#39;t quite relate to what I&#39;m trying to get across here, but feel free to prove me wrong.

I have a list of data.frames. I would like to &quot;rbind&quot; rows into another data.frame by row. In essence, all first rows form one data.frame, second rows second data.frame and so on.
Result would be a list of the same length as the number of rows in my original data.frame(s). So far, the data.frames are identical in dimensions.

Here&#39;s some data to play around with.

    sample.list &lt;- list(data.frame(x = sample(1:100, 10), y = sample(1:100, 10), capt = sample(0:1, 10, replace = TRUE)),
    		data.frame(x = sample(1:100, 10), y = sample(1:100, 10), capt = sample(0:1, 10, replace = TRUE)),
    		data.frame(x = sample(1:100, 10), y = sample(1:100, 10), capt = sample(0:1, 10, replace = TRUE)),
    		data.frame(x = sample(1:100, 10), y = sample(1:100, 10), capt = sample(0:1, 10, replace = TRUE)),
    		data.frame(x = sample(1:100, 10), y = sample(1:100, 10), capt = sample(0:1, 10, replace = TRUE)),
    		data.frame(x = sample(1:100, 10), y = sample(1:100, 10), capt = sample(0:1, 10, replace = TRUE)),
    		data.frame(x = sample(1:100, 10), y = sample(1:100, 10), capt = sample(0:1, 10, replace = TRUE)))

Here&#39;s what I&#39;ve come up with with the good ol&#39; for loop.

    #solution 1
    my.list &lt;- vector(&quot;list&quot;, nrow(sample.list[[1]]))
    for (i in 1:nrow(sample.list[[1]])) {
    	for (j in 1:length(sample.list)) {
    		my.list[[i]] &lt;- rbind(my.list[[i]], sample.list[[j]][i, ])
    	}
    }

    #solution 2 (so far my favorite)
    sample.list2 &lt;- do.call(&quot;rbind&quot;, sample.list)
    my.list2 &lt;- vector(&quot;list&quot;, nrow(sample.list[[1]]))
    
    for (i in 1:nrow(sample.list[[1]])) {
    	my.list2[[i]] &lt;- sample.list2[seq(from = i, to = nrow(sample.list2), by = nrow(sample.list[[1]])), ]
    }

Can this be improved using vectorization without much brainhurt? Correct answer will contain a snippet of code, of course. &quot;Yes&quot; as an answer doesn&#39;t count.

*EDIT*

    #solution 3 (a variant of solution 2 above)
    ind &lt;- rep(1:nrow(sample.list[[1]]), times = length(sample.list))
    my.list3 &lt;- split(x = sample.list2, f = ind)

*BENCHMARKING*

I&#39;ve made my list larger with more rows per data.frame. I&#39;ve benchmarked the results which are as follows:

    #solution 1
    system.time(for (i in 1:nrow(sample.list[[1]])) {
    	for (j in 1:length(sample.list)) {
    		my.list[[i]] &lt;- rbind(my.list[[i]], sample.list[[j]][i, ])
    	}
    })
       user  system elapsed 
     80.989   0.004  81.210 

    # solution 2
    system.time(for (i in 1:nrow(sample.list[[1]])) {
    	my.list2[[i]] &lt;- sample.list2[seq(from = i, to = nrow(sample.list2), by = nrow(sample.list[[1]])), ]
    })
       user  system elapsed 
      0.957   0.160   1.126 

    # solution 3
    system.time(split(x = sample.list2, f = ind))
       user  system elapsed 
      1.104   0.204   1.332 

    # solution Gabor
    system.time(lapply(1:nr, bind.ith.rows))
       user  system elapsed 
      0.484   0.000   0.485 

    # solution ncray
    system.time(alply(do.call(&quot;cbind&quot;,sample.list), 1,
    				.fun=matrix, ncol=ncol(sample.list[[1]]), byrow=TRUE,
    				dimnames=list(1:length(sample.list),names(sample.list[[1]]))))
       user  system elapsed 
     11.296   0.016  11.365



Fast vectorized merge of list of data.frames by row

What the difference between the float and integer data type when size is same?

What is the difference between the float and integer data type when the size is the same?

How would I go about doing arithmetic, + - / * % !,  with arbitrarily large integers without using `java.math.BigInteger`?

For instance, the factorial of 90 returns 0 in Java.
I would like to be able to solve that.

How to handle very large numbers in Java without using java.math.BigInteger

How can I convert a `String` to an `int`?

```
&quot;1234&quot;  →  1234
```


How do I convert a String to an int in Java?

I have the following in my application controller:

    def is_number?(object)
      true if Float(object) rescue false
    end

and the following condition in my controller:

    if mystring.is_number?
    
    end

The condition is throwing an `undefined method` error. I&#39;m guessing I&#39;ve defined `is_number` in the wrong place...?

Test if string is a number in Ruby on Rails

I want to limit a number between two values, I know that in PHP you can do this:


    $number = min(max(intval($number), 1), 20);
    // this will make $number 1 if it&#39;s lower than 1, and 20 if it&#39;s higher than 20


How can I do this in javascript, without having to write multiple `if` statements and stuff like that? Thanks.

How can I use JavaScript to limit a number between a min/max value?

I need to convert a multi-row two-column `data.frame` to a named character vector. 
My `data.frame` would be something like:

    dd = data.frame(crit = c(&quot;a&quot;,&quot;b&quot;,&quot;c&quot;,&quot;d&quot;), 
                    name = c(&quot;Alpha&quot;, &quot;Beta&quot;, &quot;Caesar&quot;, &quot;Doris&quot;)
                    )

and what I actually need would be:

    whatiwant = c(&quot;a&quot; = &quot;Alpha&quot;,
                  &quot;b&quot; = &quot;Beta&quot;,
                  &quot;c&quot; = &quot;Caesar&quot;,
                  &quot;d&quot; = &quot;Doris&quot;)

Converting two columns of a data frame to a named vector

in Dart, there&#39;s a convenient way to convert a String to an int:

&lt;!-- language-all: lang-dart --&gt;

    int i = int.parse(&#39;123&#39;);

is there something similar for converting bools?

    bool b = bool.parse(&#39;true&#39;);



Content Type	Original Author	Original Content on Stackoverflow
Question	Jeff Erickson	View Question on Stackoverflow
Solution 1 - R	Aaron left Stack Overflow	View Answer on Stackoverflow
Solution 2 - R	Gavin Simpson	View Answer on Stackoverflow

Convert factor to integer

R Problem Overview

R Solutions

Solution 1 - R

Solution 2 - R

About clustered index in postgres

difference between "void 0 " and "undefined"

Attributions