I usually start out with some combination of:

    typeof(obj)
    class(obj)
    sapply(obj, class)
    sapply(obj, attributes)
    attributes(obj)
    names(obj)

as appropriate based on what&#39;s revealed.  For example, try with:

    obj &lt;- data.frame(a=1:26, b=letters)
    obj &lt;- list(a=1:26, b=letters, c=list(d=1:26, e=letters))
    data(cars)
    obj &lt;- lm(dist ~ speed, data=cars)

..etc.

If `obj` is an S3 or S4 object, you can also try `methods` or `showMethods`, `showClass`, etc.  Patrick Burns&#39; [R Inferno](http://www.burns-stat.com/pages/Tutor/R_inferno.pdf) has a pretty good section on this (sec #7).

**EDIT**: Dirk and Hadley mention `str(obj)` in their answers.  It really is much better than any of the above for a quick and even detailed peek into an object.

    str(x)

It&#39;s all you need to remember for 99% of cases.

If I get &#39;someObject&#39;, say via

    someObject &lt;- myMagicFunction(...)

then I usually proceed by

    class(someObject)
    str(someObject)

which can be followed by head(), summary(), print(), ... depending on the class you have.


    attributes(someObject) 

Can also be useful

I am attempting to retrieve and set the selected value of a select element (drop down list) with jQuery.

for retrievel i have tried `$(&quot;#myId&quot;).find(&#39;:selected&#39;).val()`, as well as `$(&quot;#myId&quot;).val()` but both return undefined.

Any insight into this problem would be much appreciated.



jQuery to retrieve and set selected option value of html select element

I need to store a U.S. $ dollar amount in a field of a Django model.  What is the best model field type to use?  I need to be able to have the user enter this value (with error checking, only want a number accurate to cents), format it for output to users in different places, and use it to calculate other numbers.

What is the best django model field to use to represent a US dollar amount?

I am often ending up with a function producing output for which I don&#39;t understand the output data type. I&#39;m expecting a list and it ends up being a list of lists or a data frame or something else. What&#39;s a good method or workflow for figuring out the output data type when first using a function?

R object identification

<p>I am often ending up with a function producing output for which I don't understand the output data type. I'm expecting a list and it ends up being a list of lists or a data frame or something else. What's a good method or workflow for figuring out the output data type when first using a function?</p>


I have always found startup profile files of other people both useful and instructive about the language. Moreover, while I have some customization for [Bash][1] and [Vim][2], I have nothing for R.

For example, one thing I always wanted is different colors for input and output text in a window terminal, and maybe even syntax highlighting.

  [1]: https://en.wikipedia.org/wiki/Bash_%28Unix_shell%29
  [2]: https://en.wikipedia.org/wiki/Vim_%28text_editor%29




Expert R users, what&#39;s in your .Rprofile?

I have a data frame containing a `factor`. When I create a subset of this dataframe using `subset` or another indexing function, a new data frame is created.  However, the `factor` variable retains all of its original levels, even when/if they do not exist in the new dataframe.

This causes problems when doing faceted plotting or using functions that rely on factor levels.

What is the most succinct way to remove levels from a factor in the new dataframe?
 
Here&#39;s an example:
    
    df &lt;- data.frame(letters=letters[1:5],
                        numbers=seq(1:5))

    levels(df$letters)
    ## [1] &quot;a&quot; &quot;b&quot; &quot;c&quot; &quot;d&quot; &quot;e&quot;
    
    subdf &lt;- subset(df, numbers &lt;= 3)
    ##   letters numbers
    ## 1       a       1
    ## 2       b       2
    ## 3       c       3    

    # all levels are still there!
    levels(subdf$letters)
    ## [1] &quot;a&quot; &quot;b&quot; &quot;c&quot; &quot;d&quot; &quot;e&quot;

Drop unused factor levels in a subsetted data frame

I (sort of) already know the answer to this question.  But I figured it is one that gets asked so frequently on the R Users list, that there should be one solid good answer.  **To the best of my knowledge there is no multiline comment functionality in R.  So, does anyone have any good workarounds?**

While quite a bit of work in R usually involves interactive sessions (which casts doubt on the need for multiline comments), there are times when I&#39;ve had to send scripts to colleagues and classmates, much of which involves nontrivial blocks of code.  And for people coming from other languages it is a fairly natural question.  

In the past I&#39;ve used quotes. Since strings support linebreaks, running an R script with

    &quot;
    Here&#39;s my multiline comment.
    
    &quot;
    a &lt;- 10
    rocknroll.lm &lt;- lm(blah blah blah)
     ...

works fine.  Does anyone have a better solution?



Multiline Comment Workarounds?

I am poking into the manuals, I wanted to ask the community:
How can we set global variables inside a function?

Global variables in R

I&#39;m trying to generate a histogram in R with a logarithmic scale for y. Currently I do:

    hist(mydata$V3, breaks=c(0,1,2,3,4,5,25))

This gives me a histogram, but the density between 0 to 1 is so great (about a million values difference) that you can barely make out any of the other bars.

Then I&#39;ve tried doing:

    mydata_hist &lt;- hist(mydata$V3, breaks=c(0,1,2,3,4,5,25), plot=FALSE)
    plot(rpd_hist$counts, log=&quot;xy&quot;, pch=20, col=&quot;blue&quot;)

It gives me sorta what I want, but the bottom shows me the values 1-6 rather than 0, 1, 2, 3, 4, 5, 25.  It&#39;s also showing the data as points rather than bars. `barplot` works but then I don&#39;t get any bottom axis.

Histogram with Logarithmic Scale and custom breaks

I have this:

    List&lt;object&gt; nodes = new List&lt;object&gt;(); 
    
    nodes.Add(
    new {
    	Checked		= false,
    	depth		= 1,
    	id			= &quot;div_&quot; + d.Id
    });


... and I&#39;m wondering if I can then grab the &quot;Checked&quot; property of the anonymous object.  I&#39;m not sure if this is even possible.  Tried doing this:

`if (nodes.Any(n =&gt; n[&quot;Checked&quot;] == false))`  ... but it doesn&#39;t work.

Thanks




How to access property of anonymous type in C#?

What is a class, an object and an instance in Java?

The difference between Classes, Objects, and Instances

I want to know the size occupied by a JavaScript object.

Take the following function:

    function Marks(){
      this.maxMarks = 100;
    }
    
    function Student(){
      this.firstName = &quot;firstName&quot;;
      this.lastName = &quot;lastName&quot;;
      this.marks = new Marks();
    }

Now I instantiate the `student`:

    var stud = new Student();

so that I can do stuff like

    stud.firstName = &quot;new Firstname&quot;;
    
    alert(stud.firstName);
    
    stud.marks.maxMarks = 200;

etc.

Now, the `stud` object will occupy some size in memory. It has some data and more objects.

How do I find out how much memory the `stud` object occupies? Something like a `sizeof()` in JavaScript? It would be really awesome if I could find it out in a single function call like `sizeof(stud)`.

I’ve been searching the Internet for months—couldn’t find it (asked in a couple of forums—no replies).

How to get the size of a JavaScript object?

I&#39;m searching for an elegant way to get data using attribute access on a dict with some nested dicts and lists (i.e. javascript-style object syntax).

For example:

    &gt;&gt;&gt; d = {&#39;a&#39;: 1, &#39;b&#39;: {&#39;c&#39;: 2}, &#39;d&#39;: [&quot;hi&quot;, {&#39;foo&#39;: &quot;bar&quot;}]}

Should be accessible in this way:

    &gt;&gt;&gt; x = dict2obj(d)
    &gt;&gt;&gt; x.a
    1
    &gt;&gt;&gt; x.b.c
    2
    &gt;&gt;&gt; x.d[1].foo
    bar

I think, this is not possible without recursion, but what would be a nice way to get an object style for dicts?

Convert nested Python dict to object?

What is more efficient in Python in terms of memory usage and CPU consumption - Dictionary or Object?

**Background:**
I have to load huge amount of data into Python. I created an object that is just a field container. Creating 4M instances and putting them into a dictionary took about 10 minutes and ~6GB of memory. After dictionary is ready, accessing it is a blink of an eye.

**Example:**
To check the performance I wrote two simple programs that do the same - one is using objects, other dictionary:

Object (execution time ~18sec):

    class Obj(object):
      def __init__(self, i):
        self.i = i
        self.l = []
    all = {}
    for i in range(1000000):
      all[i] = Obj(i)

Dictionary (execution time ~12sec):

    all = {}
    for i in range(1000000):
      o = {}
      o[&#39;i&#39;] = i
      o[&#39;l&#39;] = []
      all[i] = o

**Question:**
Am I doing something wrong or dictionary is just faster than object? If indeed dictionary performs better, can somebody explain why?





Content Type	Original Author	Original Content on Stackoverflow
Question	JD Long	View Question on Stackoverflow
Solution 1 - R	ars	View Answer on Stackoverflow
Solution 2 - R	hadley	View Answer on Stackoverflow
Solution 3 - R	Dirk Eddelbuettel	View Answer on Stackoverflow
Solution 4 - R	Josh Reich	View Answer on Stackoverflow

R object identification

R Problem Overview

R Solutions

Solution 1 - R

Solution 2 - R

Solution 3 - R

Solution 4 - R

What is the best django model field to use to represent a US dollar amount?

jQuery to retrieve and set selected option value of html select element

Attributions