Courtesy of the `?strptime` help file (with the example changed to your value):

     z &lt;- strptime(&quot;2010-01-15 13:55:23.975&quot;, &quot;%Y-%m-%d %H:%M:%OS&quot;)
     z # prints without fractional seconds
     op &lt;- options(digits.secs=3)
     z
     options(op) #reset options


You can also use `strptime(time[1], &quot;%OSn&quot;)` where 0 &lt;= n &lt;= 6, without having to set `digits.secs`.

The documentation states &quot;Which of these are supported is OS-dependent.&quot; so YMMV.

I&#39;ve noticed that, occasionally, when I use &lt;kbd&gt;O&lt;/kbd&gt; (capital &#39;o&#39;) to create a new line and go into insert mode, there is a short delay before anything happens.

Is this common? Is there any way to change it?

Both `:map O` and `:imap O` show &quot;No mapping found&quot;, so I don&#39;t think it&#39;s a strange mapping.

Delay before &#39;O&#39; opens a new line?

I have a C# dictionary, `Dictionary&lt;Guid, MyObject&gt;` that I need to be filtered based on a property of `MyObject`.

For example, I want to remove all records from the dictionary where `MyObject.BooleanProperty = false`. What is the best way of acheiving this?

Filtering out values from a C# Generic Dictionary

How do I use `strptime` or any other functions to parse time stamps with milliseconds in R?

    time[1]
    # [1] &quot;2010-01-15 13:55:23.975&quot;
    strptime(time[1], format=&quot;%Y-%m-%d %H:%M:%S.%f&quot;)
    # [1] NA
    strptime(time[1], format=&quot;%Y-%m-%d %H:%M:%S&quot;)
    # [1] &quot;2010-01-15 13:55:23&quot;`


How to parse milliseconds?

How do I use <code>strptime</code> or any other functions to parse time stamps with milliseconds in R?
<pre><code class="hljs language-perl">time[1]
# [1] "2010-01-15 13:55:23.975"
strptime(time[1], format="%Y-%m-%d %H:%M:%S.%f")
# [1] NA
strptime(time[1], format="%Y-%m-%d %H:%M:%S")
# [1] "2010-01-15 13:55:23"`
</code></pre>

I&#39;ve got a R script for which I&#39;d like to be able to supply several command-line parameters (rather than hardcode parameter values in the code itself).  The script runs on Windows.

I can&#39;t find info on how to read parameters supplied on the command-line into my R script.  I&#39;d be surprised if it can&#39;t be done, so maybe I&#39;m just not using the best keywords in my Google search...

Any pointers or recommendations?

How can I read command line parameters from an R script?

my R code ends up containing plethora of statements of the form:

    if (!is.null(aVariable)) { 
         do whatever 
    }

But this kind of statement is hard to read because it contains two negations. I would prefer something like: 

     if (is.defined(aVariable)) { 
          do whatever 
     }

Does a `is.defined` type function that does the opposite of !is.null exist standard in R?

cheers,
yannick



alternative to &quot;!is.null()&quot; in R

Is there some way to use a specific small image as a point in a scatterplot with ggplot2.  Ideally I will want to resize the images based on an variable.

Here&#39;s an example:

    library(ggplot2)
    p &lt;- ggplot(mtcars, aes(wt, mpg))
    p + geom_point(aes(size = qsec, shape = factor(cyl)))

So I basically want to know if there is a way to supply a specific image as the shape?


How to use an image as a point in ggplot?

I have some trouble to convert my `data.frame` from a wide table to a long table.
At the moment it looks like this:

    Code Country        1950	1951	1952	1953	1954
    AFG  Afghanistan    20,249  21,352  22,532  23,557  24,555
    ALB  Albania        8,097   8,986   10,058  11,123  12,246

Now I would like to transform this `data.frame` into a long `data.frame`.
Something like this:

    Code Country        Year	Value
    AFG  Afghanistan    1950	20,249
    AFG  Afghanistan    1951	21,352
    AFG  Afghanistan    1952	22,532
    AFG  Afghanistan    1953	23,557
    AFG  Afghanistan    1954	24,555
    ALB  Albania        1950	8,097
    ALB  Albania        1951	8,986
    ALB  Albania        1952	10,058
    ALB  Albania        1953	11,123
    ALB  Albania        1954	12,246

I have looked at and already tried using the `melt()` and the `reshape()` functions
as some people were suggesting in similar questions.
However, so far I only get messy results.

If it is possible I would like to do it with the `reshape()` function since
it looks a little bit nicer to handle.



Reshaping data.frame from wide to long format

In R, what is the most efficient/idiomatic way to count the number of `TRUE` values in a logical vector? I can think of two ways:

    z &lt;- sample(c(TRUE, FALSE), 1000, rep = TRUE)
    sum(z)
    # [1] 498
    
    table(z)[&quot;TRUE&quot;]
    # TRUE 
    #  498 

Which do you prefer? Is there anything even better?

How to count TRUE values in a logical vector

I have a file. In Python, I would like to take its creation time, and convert it to an [ISO time (ISO 8601) string][1] **while preserving the fact that it was created in the [Eastern Time Zone][2] (ET)**.

How do I take the file&#39;s ctime and convert it to an ISO time string that indicates the Eastern Time Zone (and takes into account daylight savings time, if necessary)?

  [1]: http://en.wikipedia.org/wiki/ISO_8601
  [2]: https://en.wikipedia.org/wiki/Eastern_Time_Zone


ISO time (ISO 8601) in Python

I would like to run a query like

    select ... as days where `date` is between &#39;2010-01-20&#39; and &#39;2010-01-24&#39;

And return data like:  
&lt;pre&gt;
days
----------
2010-01-20
2010-01-21
2010-01-22
2010-01-23
2010-01-24
&lt;/pre&gt;


generate days from date range

    t = e[&#39;updated_parsed&#39;]
    dt = datetime.datetime(t[0],t[1],t[2],t[3],t[4],t[5],t[6]
    print dt
    &gt;&gt;&gt;2010-01-28 08:39:49.000003

How do I turn that into a string?:

    &quot;January 28, 2010&quot;

How do I turn a python datetime into a string, with readable format date?

Is there a simple way to convert one date format into another date format in PHP?

I have this:

    $old_date = date(&#39;y-m-d-h-i-s&#39;);            // works

    $middle = strtotime($old_date);             // returns bool(false)
    
    $new_date = date(&#39;Y-m-d H:i:s&#39;, $middle);   // returns 1970-01-01 00:00:00

But I&#39;d of course like it to return a current date rather than the crack &#39;o dawn. What am I doing wrong?

Convert one date format into another in PHP

I want to be sure that if I commit something in Subversion from one machine, and I checkout on another, I will get the same value for datetime and timestamp.

Currently, I observed that the datetime of file&#39;s modification is from the moment when I did the synchronisation instead of the original value.

For me, it doesn&#39;t make any sense to know when the files were synchronised - I just want to see the last commit time.

This issue is not timezone related.

How can I keep the original file [commit] timestamp on Subversion?

A very newbish question, but say I have data like this:

    test_data &lt;-
      data.frame(
        var0 = 100 + c(0, cumsum(runif(49, -20, 20))),
        var1 = 150 + c(0, cumsum(runif(49, -10, 10))),
        date = seq(as.Date(&quot;2002-01-01&quot;), by=&quot;1 month&quot;, length.out=100)
      )

How can I plot both time series `var0` and `var1` on the same graph, with `date` on the x-axis, using `ggplot2`?  Bonus points if you make `var0` and `var1` different colours, and can include a legend!

I&#39;m sure this is very simple, but I can&#39;t find any examples out there.

Plotting two variables as lines using ggplot2 on the same graph

I&#39;m trying to convert a data frame to xts object using the as.xts()-method. Here is my input dataframe q:

    q
                          t x  
    1  2006-01-01 00:00:00  1  
    2  2006-01-01 01:00:00  2  
    3  2006-01-01 02:00:00  3

    str(q)
        &#39;data.frame&#39;:   10 obs. of  2 variables:
     $ t: POSIXct, format: &quot;2006-01-01 00:00:00&quot; &quot;2006-01-01 01:00:00&quot; &quot;2006-01-01 02:00:00&quot; &quot;2006-01-01 03:00:00&quot; ...  
     $ x: int  1 2 3 4 5 6 7 8 9 10

The result is:

    &gt; as.xts(q)
    Error in as.POSIXlt.character(x, tz, ...) : 
      character string is not in a standard unambiguous format

This is the simplest example I can think of, so it&#39;s quite frustrating not getting it to work... Any help is appreciated!

Converting a data frame to xts

I am creating a system which polls devices for data on varying metrics such as CPU utilisation, disk utilisation, temperature etc. at (probably) 5 minute intervals using SNMP. The ultimate goal is to provide visualisations to a user of the system in the form of time-series graphs.

I have looked at using RRDTool in the past, but rejected it as storing the captured data indefinitely is important to my project, and I want higher level and more flexible access to the captured data. So my question is really:

*What is better, a relational database (such as MySQL or PostgreSQL) or a non-relational or NoSQL database (such as MongoDB or Redis) with regard to performance when querying data for graphing.*

## Relational

Given a relational database, I would use a `data_instances` table, in which would be stored every instance of data captured for every metric being measured for all devices, with the following fields:

Fields: `id` `fk_to_device` `fk_to_metric` `metric_value` `timestamp`

When I want to draw a graph for a particular metric on a particular device, I must query this singular table *filtering out* the other devices, and the other metrics being analysed for this device:

    SELECT metric_value, timestamp FROM data_instances
        WHERE fk_to_device=1 AND fk_to_metric=2

The number of rows in this table would be:

    d * m_d * f * t

where `d` is the number of **devices**, `m_d` is the accumulative **number of metrics** being recorded for all devices, `f` is the **frequency** at which data is polled for and `t` is the total amount of **time** the system has been collecting data.

For a user recording 10 metrics for 3 devices every 5 minutes for a year, we would have just under **5 million** records. 

### Indexes

Without indexes on `fk_to_device` and `fk_to_metric` scanning this continuously expanding table would take too much time. So indexing the aforementioned fields and also `timestamp` (for creating graphs with localised periods) is a requirement.

## Non-Relational (NoSQL)

MongoDB has the concept of a *collection*, unlike tables these can be created programmatically without setup. With these I could partition the storage of data for each device, or even each metric recorded for each device.

I have no experience with NoSQL and do not know if they provide any query performance enhancing features such as indexing, however the previous paragraph proposes doing most of the traditional relational query work in the structure by which the data is stored under NoSQL.

## Undecided

Would a relational solution with correct indexing reduce to a crawl within the year? Or does the collection based structure of NoSQL approaches (which matches my mental model of the stored data) provide a noticeable benefit?

Storing time-series data, relational or non?

Even though I found Hadley&#39;s post in the google group on `POSIXct` and `geom_vline`, I could not get it done. I have a time series from and would like to draw a vertical line for years 1998, 2005 and 2010 for example. I tried with `ggplot` and `qplot` syntax, but still I either see no vertical line at all or the vertical line is drawn at the very first vertical grid and the whole series is shifted somewhat strangely to the right.

    gg &lt;- ggplot(data=mydata,aes(y=somevalues,x=datefield,color=category)) +
          layer(geom=&quot;line&quot;)
    gg + geom_vline(xintercept=mydata$datefield[120],linetype=4)
    # returns just the time series plot I had before, 
    # interestingly the legend contains dotted vertical lines

My date field has format &quot;1993-07-01&quot; and is of class `Date`.

How to get a vertical geom_vline to an x-axis of class date?

Are there any lossless compression methods that can be applied to floating point time-series data, and will significantly outperform, say, writing the data as binary into a file and running it through gzip?

Reduction of precision might be acceptable, but it must happen in a controlled way (i.e. I must be able to set a bound on how many digits must be kept)

I am working with some large data files which are series of correlated `double`s, describing a function of time (i.e. the values are correlated).  I don&#39;t generally need the full `double` precision but I might need more than `float`.

Since there are specialized lossless methods for images/audio, I was wondering if anything specialized exists for this situation.

**Clarification:**  I am looking for existing practical tools rather than a paper describing how to implement something like this.  Something comparable to gzip in speed would be excellent. 

Compressing floating point data

Please consider the following

    $ R --vanilla

    &gt; as.Date(&quot;01 Jan 2000&quot;)
    Error in charToDate(x) :
        character string is not in a standard unambiguous format

But that date clearly *is* in a standard unambiguous format. Why the error message?

Worse, an ambiguous date is apparently accepted without warning or error and then read incorrectly!

    &gt; as.Date(&quot;01/01/2000&quot;)
    [1] &quot;0001-01-20&quot;

I&#39;ve searched and found 28 other questions in the [R] tag containing this error message. All with solutions and workarounds involving specifying the format, iiuc. This question is different in that I&#39;m asking where are the standard unambiguous formats defined anyway, and can they be changed?  Does everyone get these messages or is it just me? Perhaps it is locale related?

In other words, is there a better solution than needing to specify the format?

[29 questions containing &quot;[R] standard unambiguous format&quot;][1]

    &gt; sessionInfo()
    R version 2.15.2 (2012-10-26)
    Platform: x86_64-w64-mingw32/x64 (64-bit)
    
    locale:
    [1] LC_COLLATE=English_United Kingdom.1252
    [2] LC_CTYPE=English_United Kingdom.1252
    [3] LC_MONETARY=English_United Kingdom.1252
    [4] LC_NUMERIC=C
    [5] LC_TIME=English_United Kingdom.1252
    
    attached base packages:
    [1] stats     graphics  grDevices utils     datasets  methods   base

  [1]: https://stackoverflow.com/search?q=%5Br%5D%20standard%20unambiguous%20format

What are the &quot;standard unambiguous date&quot; formats for string-to-date conversion in R?

Please what&#39;s wrong with my code: 

    import datetime
    d = &quot;2013-W26&quot;
    r = datetime.datetime.strptime(d, &quot;%Y-W%W&quot;)
    print(r)

Display &quot;2013-01-01 00:00:00&quot;, Thanks.

Get date from week number

I have three date formats: `YYYY-MM-DD`, `DD.MM.YYYY`, `DD/MM/YYYY`.

Is it possible to validate and parse strings such as `2014-05-18` or `18.5.2014` or `18/05/2019`?

How to format date string via multiple formats in python

I have a date string and want to convert it to the date type:

I have tried to use datetime.datetime.strptime with the format that I want but it is returning the time with the conversion.

        when = alldates[int(daypos[0])]
        print when, type(when)

        then = datetime.datetime.strptime(when, &#39;%Y-%m-%d&#39;)
        print then, type(then)

This is what the output returns:

       2013-05-07 &lt;type &#39;str&#39;&gt;
       2013-05-07 00:00:00 &lt;type &#39;datetime.datetime&#39;&gt;

I need to remove the the time: 00:00:00.

Display Python datetime without time

Is there a way to parse timezone in &quot;+00:00&quot; format with `datetime.strptime`? For instance:

    Python 3.4.3 (v3.4.3:9b73f1c3e601, Feb 24 2015, 22:43:06) [MSC v.1600 32 bit (In
    tel)] on win32
    Type &quot;help&quot;, &quot;copyright&quot;, &quot;credits&quot; or &quot;license&quot; for more information.
    &gt;&gt;&gt; from datetime import datetime
    &gt;&gt;&gt; datetime.strptime(&quot;12:34:56+0000&quot;, &quot;%X%z&quot;)
    datetime.datetime(1900, 1, 1, 12, 34, 56, tzinfo=datetime.timezone.utc)
    &gt;&gt;&gt; datetime.strptime(&quot;12:34:56+00:00&quot;, &quot;%X%z&quot;)
    Traceback (most recent call last):
      File &quot;&lt;stdin&gt;&quot;, line 1, in &lt;module&gt;
      File &quot;C:\Python34\lib\_strptime.py&quot;, line 500, in _strptime_datetime
        tt, fraction = _strptime(data_string, format)
      File &quot;C:\Python34\lib\_strptime.py&quot;, line 337, in _strptime
        (data_string, format))
    ValueError: time data &#39;12:34:56+00:00&#39; does not match format &#39;%X%z&#39;

Any ideas?

Content Type	Original Author	Original Content on Stackoverflow
Question	signalseeker	View Question on Stackoverflow
Solution 1 - R	Aniko	View Answer on Stackoverflow
Solution 2 - R	user244343	View Answer on Stackoverflow

How to parse milliseconds?

R Problem Overview

R Solutions

Solution 1 - R

Solution 2 - R

Filtering out values from a C# Generic Dictionary

Delay before 'O' opens a new line?

Attributions