How can one produce an ISO date string "yyyy-MM-dd" from a Q date type? I looked at concatenating the various parts but am not even able to get the day/month, e.g. d:2015.12.01;d.month prints 2015.12, i.e. more than just the month.
If you plan to do it on a large scale (i.e. a large vector/list of dates or a column in a table) and you're sure your dates are always well-formed, then you could use a dot-amend:
q)update .[;(::;4 7);:;"-"]string date from ([] date:2#.z.D)
date
------------
"2016-01-04"
"2016-01-04"
This way you wouldn't have to apply to "each" entry of the vector/list, it works on the vector/list itself.
q)"-" sv "." vs string[2015.12.01]
"2015-12-01"
vs vector from string, splits by "." above;
sv string to vector, join by "-" above.
Remember a string is just a char array, so you can grab each part as you require with indexing. But the above is useful as the resulting vector of vs gives a 3-length vector that you manipulate any way you like
I believe the shortest (and cleanest) option for ISO8601 UTC timestamp available since at least kdb v3.4 would be to use .h.iso8601 builtin
i.e.
q).h.iso8601 .z.p
"2020-11-09T15:42:19.292301000"
Or, if you just need milliseconds similar to what JS toISOString() does, use:
q).isotime:{(23#.h.iso8601 x),"Z"}
q).isotime[.z.p]
"2020-11-09T16:02:02.601Z"
q).isotime[2015.12.01]
"2015-12-01T00:00:00.000Z"
Note .z.p is important, as .h.iso8601 .z.P would silently give you local time without timezone (+0100 etc) so it would still be interpreted as UTC by compliant ISO8601 parser :(
Check-out this GitHub library for datetime formatting. It supports the excel way of formatting date and time. It might not be the right fit for formatting a large number of objects.
q).dtf.format["yyyy-mm-dd"; 2018.06.08T01:02:03.456]
"2018-06-08"
time formatting :
q).dtf.format["yyyy-mmmm-dd hh:uu AM/PM"; 2018.01.08T01:02:03.456]
"2018-January-08 01:02 AM"
I am using something like this:
q)ymd:{[x;s](4#d),s,(2#-5#d),s,-2#d:string[x]}
q)ymd[.z.D;"-"]
"2016-01-25"
q)ymd[.z.D;"/"]
"2016/01/25"
q)ymd[.z.D;""]
"20160125"
Or for tables:
q)t:([]a:5#1;5#.z.d)
q)update s:ymd[;"-"] each d from t
a d s
-------------------------
1 2016.01.26 "2016-01-26"
1 2016.01.26 "2016-01-26"
1 2016.01.26 "2016-01-26"
1 2016.01.26 "2016-01-26"
1 2016.01.26 "2016-01-26"
Please change the separator like - or / in the update statement.
update s:{ssr[string x;".";y]}'[d;"-"] from ([]a:5#1;5?.z.d)
a d s
-------------------------
1 2010.12.31 "2010-12-31"
1 2012.08.24 "2012-08-24"
1 2004.12.05 "2004-12-05"
1 2000.10.02 "2000-10-02"
1 2006.09.10 "2006-09-10"
Related
I've looked for help on the internet for the following, but I could not find a satisfying answer: for an assignment, I need to plot the time series of a certain variable (the term spread in percentages), with years on the x-axis.
However, we use daily data. Does anybody know a convenient way in which this can be done? The 'date' variable that I've got is formulated in the following way: 20111017 represents the 17th of October 2011.
I tried to extract the first 4 numbers of the variable 'date', by using the substr(date, 1, 4) command, but the message 'type mismatch' popped up. Also, I'm not quite sure if it gives the right information if I only use the years to plot daily data (over the years). It now gives the following graph, which doesn't look that nice.
Answering the question in your title.
The date() function expects a string. If your variable with value 20111017 is in a numeric format you can convert it like this: tostring datenum , gen(datestr).
Then when using the date() function you must provide a mask that tells Stata what format the date string is in. Below is a reproducible example you can run to see how this works.
* Example generated by -dataex-. For more info, type help dataex
clear
input float datenum
20111016
end
* Convert numberic varaible to string
tostring datenum , gen(datestr)
* Convert string to date
gen date = date(datestr, "YMD")
* Display date as date
format date %td
If this does not help you, try to provide a reproducible example.
This adds some details to the helpful answer by #TheIceBear.
As he indicates, one way to get a Stata daily date from your run-together date variable is convert it to a string first. But tostring is just one way to do that and not essential. (I have nothing against tostring, as its original author, but it is better suited to other tasks.)
Here I use daily() not date(): the results are identical, but it's a good idea to use daily(): date() is all too often misunderstood as a generic date function, whereas all it does is produce daily dates (or missings).
To get a numeric year variable, just divide by 10000 and round down. You could convert to a string, extract the first 4 characters, and then convert to numeric, but that's more operations.
clear
set obs 1
gen long date = 20111017
format date %8.0f
gen ddate = daily(strofreal(date, "%8.0f"), "YMD")
format %td ddate
gen year = floor(date/10000)
list
+-----------------------------+
| date ddate year |
|-----------------------------|
1. | 20111017 17oct2011 2011 |
+-----------------------------+
* date is in %td format
gen date1 = real(string(mofd(daily(date, "DMY")), "%tmCYN"))
* type mismatch error
tostring date, gen(dt)
gen date1 = real(string(mofd(daily(dt, "DMY")), "%tmCYN"))
* the code runs but generates no results
tostring date, gen(dt)
gen date2=date(dt, "YMD")
* the code runs but generates no results
If a date variable has a display format %td it must be numeric and stored as some kind of integer. The display format is, and is only, an instruction to Stata on how to display such integers. Confusions about conversion often seem to hinge on a misunderstanding about what format means, as format is an overloaded word in computing, referring variously to file format (as in graphics file format, .png or jpg or whatever); data layout (as in wide or long layout, structure or format); variable or storage type; and (here) display format. There could well be yet other meanings.
A date displayed as 30jan2015 is stored as an integer, namely
. display mdy(1, 30, 2015)
20118
and a glance at help data types shows that your variable date could be stored as an int, float, long or double. All would work, although int is least demanding of memory. You would need (e.g.) to run describe date to find out which type is being used in your case, but nothing to come in this answer depends on knowing that type. Note that finding out what Stata is doing and thinking can be illuminated by running display with simple, single examples.
Your question is ambiguous.
Want to change display format? If you wish merely to see your dates in a display format exemplified by 20150130 then consulting help datetime display formats shows that the display format is as tested here with display, which can be abbreviated all the way down to di
. di %tdCCYYNNDD 20118
20150130
so
format date %tdCCYYNNDD
is what you need. That instructs Stata to change the display format, but the numbers stored remain precisely as they were.
Want such dates as variables held as integers? If you want the dates to be held as integers like 20150130 then you could convert it to string using the display format above, and then to a real value. A minimal sandbox dataset shows this:
. clear
. set obs 1
Number of observations (_N) was 0, now 1.
. gen date = 20118
. gen wanted = real(strofreal(date, "%tdCCYYNNDD"))
. format wanted %8.0f
. l
+------------------+
| date wanted |
|------------------|
1. | 20118 20150130 |
+------------------+
A display format such as %8.0f is needed to see such values directly.
Another method is to generate a large integer directly. You need to be explicit about a suitable storage type and (as just mentioned) need to set an appropriate format, but it can be got to work:
. gen long also = 10000 * year(date) + 100 * month(date) + day(date)
. format also %8.0f
Want such dates as variables held as strings? This is the previous solution, but leave off the real(). The default display format will work fine.
. gen WANTED = strofreal(date, "%tdCCYYNNDD")
. l
+-----------------------------+
| date wanted WANTED |
|-----------------------------|
1. | 20118 20150130 20150130 |
+-----------------------------+
I have not used tostring here but as its original author I have no bias against it. The principles needed here are better illustrated using the underlying function strofreal(). The older name string() will still work.
Turning to your code,
tostring date, gen(dt)
will just put integers like 20118 in string form, so "20118", but there is no way that Stata can understand that alone to be a daily date. You could have run tostring with a format argument, which would have been equivalent to the code above. The advantage of tostring would only be if you had several such variables you wished to convert at once, as tostring would loop over such variables for you.
I can't follow why you thought that conversion to a monthly date or use of a monthly date display format was needed or helpful, as at best you'd lose the information on day of the month. Thus at best Stata can only map a monthly date back to the first day of that month, and at worst a monthly date (here 660) could not be understood as anything you want.
. di mofd(20118)
660
. di %td mofd(20118)
22oct1961
. di %td dofm(mofd(20118))
01jan2015
There is no shortcut to understanding how Stata thinks about dates that doesn't involve reading the needed parts of help datetime and help datetime display formats.
Yet more explanation and examples can be found at https://www.stata-journal.com/article.html?article=dm0067
I have a .csv file with the first column containing dates, a snippet of which looks like the following:
date,values
03/11/2020,1
03/12/2020,2
3/14/20,3
3/15/20,4
3/16/20,5
04/01/2020,6
I would like to import this data into Matlab (I think the best way would probably be using the readtable() function, see here). My goal is to bring the dates into Matlab as a datetime array. As you can see above, the problem is that the dates in the original .csv file are not consistently formatted. Some of them are in the format mm/dd/yyyy and some of them are mm/dd/yy.
Simply calling data = readtable('myfile.csv') on the .csv file results in the following, which is not correct:
'03/11/2020' 1
'03/12/2020' 2
'03/14/0020' 3
'03/15/0020' 4
'03/16/0020' 5
'04/01/2020' 6
Does anyone know a way to automatically account for this type of data in the import?
Thank you!
My version: Matlab R2017a
EDIT ---------------------------------------
Following the suggestion of Max, I have tried specifiying some of the input options for the read command using the following:
T = readtable('example.csv',...
'Format','%{dd/MM/yyyy}D %d',...
'Delimiter', ',',...
'HeaderLines', 0,...
'ReadVariableNames', true)
which results in:
date values
__________ ______
03/11/2020 1
03/12/2020 2
NaT 3
NaT 4
NaT 5
04/01/2020 6
and you can see that this is not working either.
If you are sure all the dates involved do not go back more than 100 years, you can easily apply the pivot method which was in use in the last century (before th 2K bug warned the world of the danger of the method).
They used to code dates in 2 digits only, knowing that 87 actually meant 1987. A user (or a computer) would add the missing years automatically.
In your case, you can read the full table, parse the dates, then it is easy to detect which dates are inconsistent. Identify them, correct them, and you are good to go.
With your example:
a = readtable(tfile) ; % read the file
dates = datetime(a.date) ; % extract first column and convert to [datetime]
idx2change = dates.Year < 2000 ; % Find which dates where on short format
dates.Year(idx2change) = dates.Year(idx2change) + 2000 ; % Correct truncated years
a.date = dates % reinject corrected [datetime] array into the table
yields:
a =
date values
___________ ______
11-Mar-2020 1
12-Mar-2020 2
14-Mar-2020 3
15-Mar-2020 4
16-Mar-2020 5
01-Apr-2020 6
Instead of specifying the format explicitly (as I also suggested before), one should use the delimiterImportoptions and in the case of a csv-file, use the delimitedTextImportOptions
opts = delimitedTextImportOptions('NumVariables',2,...% how many variables per row?
'VariableNamesLine',1,... % is there a header? If yes, in which line are the variable names?
'DataLines',2,... % in which line does the actual data starts?
'VariableTypes',{'datetime','double'})% as what data types should the variables be read
readtable('myfile.csv',opts)
because the neat little feature recognizes the format of the datetime automatically, as it knows that it must be a datetime-object =)
This is the given expression of GREL language on OpenRefine.
diff(date d1, date d2, optional string timeUnit)
For dates, returns the difference in given time units.
So the question is how to get the access to the values of both columns, that is not clear on presented on the documentation.
Thanks
The formula for accessing another column is:
cells.YourColumnName.value
If your column name contains spaces or non-ascii characters :
cells['Your Column Name'].value
So, assuming your two columns are named "date1" and "date2", and you want the difference in days, the GREL formula is as follows :
diff(cells.date1.value, cells.date2.value, "days")
or
diff(cells['date1'].value, cells['date2'].value, "days")
I found a way myself here is the example of the working command, the GREL documentation is not that explicit treating this procedure.
Here is the commend I used, I multiplied the result by -1 to make it positive.
diff(cells["DATA_COMPRA"].value, cells["DATA_VENCIMENTO"].value, "days") * -1
Hope that helps, I my have to come back here sometimes to get this script again and again.
I want to assign the current year in a YY format to either a macro or data set variable.
I am able to use the automatic macro variables &sysdate or &sysdate9 to get the current date. However, extracting the year in a YY format is proving to be a nightmare. Below are some examples of what I've been trying.
There exists the YEARw. format. But when I try to use it I get errors or weird results. For instance, running
data _null_;
yy = year(input("&sysdate9.", year2.));
put yy=;
run;
produces the error
ERROR 48-59: The informat YEAR was not found or could not be loaded.
If I try to format the variable in the output, I get 1965 instead of the current year. The following
data _null_;
yy = year(input("&sysdate9.", date9.));
put yy= yy year2.;
run;
outputs
yy=2016 65
Please help.
This works to get you the 2-digit year number of the current year:
DATA _NULL_;
YEAR = PUT(TODAY(),YEAR2.);
PUT YEAR;
RUN;
/* Returns: 16 */
To breakdown what I am doing here:
I use TODAY() to get the current date as a DATE type. &SASDATE needs to be converted to a DATE, but also it is the date that the SAS session started. TODAY() is the current date.
PUT allows us to pass in a non-character (numeric/date) value, which is why it is used with TODAY() as opposed to INPUT.
I think it is worth exploring the issues here in more detail.
First, Formats are patterns for converting numeric values to a human readable format. That's what you want to do here: convert a date value to a human readable format, in this case to a year.
Informats, on the other hand, convert human readable information to numeric values. That's not what you're doing here; you have a value already.
Second, put matches with Formats, and input matches with informats, exclusively.
Third, you get close in your last try: but you misuse the year format. Formats are basically value mappings, so they map every possible numeric value in their range (sometimes "all values" is the range, sometimes not) to a display value (string). You need to know what kind of value is expected on the input. YEARw. expects a date value as input, not a year value: meaning input is "number of days from 1/1/1960", mapped to "year". So you cannot take a value you've already mapped to a year value and map it again with that method; it will not make any sense.
Let's look at it:
data _null_;
yy = year(input("&sysdate9.", date9.));
put yy= yy year2.;
run;
yy contains the result of the year function - 2016. Good so far. Now, you need the 2 digit year (16); you can get that through mod function, if you like, or put/substr/input:
data _null_;
yy = input(substr(put(year(input("&sysdate9.", date9.)),4.),3,2),2.);
put yy=;
run;
mod is probably easier though since it's a number. But of course you could've used year:
data _null_;
yy = put(input("&sysdate9.", date9.),year2.);
put yy=;
run;
Now, yy is character, so you could wrap that with input(...,2.) or leave it character depending on your purposes.
Finally - a use note on &sysdate9.. You can easily make this a date without input:
"&sysdate9."d
So:
yy = put("&sysdate9."d,year2.);
That's called a date literal (and "..."dt and "..."t also work for datetime,time). They require things in the standard SAS formats to work properly.
And as pointed out in Nicarus' answer, today() is a bit better than &sysdate9 since it is guaranteed to be today. If you're running this in batch or restart your session daily, this won't matter, but it will if you have a long-running session.
Apply the year function to the date variable
Convert to string
Take last 2 digits
EDIT: change input to PUT
Year = substr(put(year(today()), 4.), 3);