I am new to mongo and not a JavaScript ninja so forgive my silliness. That said, I am looking to perform a mapreduce on a set of events to get counts by day of the week (i.e. What day of the week is most popular for events?) My efforts have left me short around how to extract the day of week (or month of year) from a date inside the mapReduce function. My solution thus far looks as follows:
> var day = value.date.getDay; // Here seems to be the sticky bit
> if (day == 0) {
> retVal.su += value.su;
> }...{
> } else {
> retVal.sa += value.sa;
> }
> });
> return retVal;
> }
> db.runCommand({
> mapReduce: "track_event",
> map: mapFunction,
> reduce: reduceFunction,
> out: "myOutput"
> });
I have been poking around here and other places a bit and have found date operations like this seem to yet be a bit limiting. So if someone can put me down a more correct path I'd appreciate any advice moving forward.
> var now = new Date()
> now.getDay()
4
> now.getMonth()
5
Remember these are 0 based.
Also, don't forget to copy the date to your retVal object as you are
creating a new Date here:
var retVal = { count:0, date:new Date(), su:0, m:0, t:0, w:0, r:0, f:0, sa:0 };
On Thu, Jun 21, 2012 at 4:57 PM, Brad Karels <bkar...@gmail.com> wrote:
> I am new to mongo and not a JavaScript ninja so forgive my silliness. That
> said, I am looking to perform a mapreduce on a set of events to get counts
> by day of the week (i.e. What day of the week is most popular for events?)
> My efforts have left me short around how to extract the day of week (or
> month of year) from a date inside the mapReduce function. My solution thus
> far looks as follows:
>>> var day = value.date.getDay; // Here seems to be the sticky bit
>>> if (day == 0) {
>>> retVal.su += value.su;
>>> }...{
>>> } else {
>>> retVal.sa += value.sa;
>>> }
>>> });
>>> return retVal;
>>> }
>>> db.runCommand({
>>> mapReduce: "track_event",
>>> map: mapFunction,
>>> reduce: reduceFunction,
>>> out: "myOutput"
>>> });
> I have been poking around here and other places a bit and have found date
> operations like this seem to yet be a bit limiting. So if someone can put
> me down a more correct path I'd appreciate any advice moving forward.
> Thank you.
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2) I think that you should be checking for the specific day of the week in your map() function, and not in the reduce() function. Remember, the reduce() function is only used to accumulate what's been emitted by the map() function.
Here is the code that I used to get the correct results for your problem:
map = function() { var day = this.date.getDay(); var ret = { count: 1, su:0, mo:0, tu:0, we:0, th:0, fr:0, sa:0, }; if ( day == 0 ) ret.su++; if ( day == 1 ) ret.mo++; if ( day == 2 ) ret.tu++; if ( day == 3 ) ret.we++; if ( day == 4 ) ret.th++; if ( day == 5 ) ret.fr++; if ( day == 6 ) ret.sa++; emit({ event: this.event }, ret );
}
reduce = function(key, values) { var ret = { count:0, su:0, mo:0, tu:0, we:0, th:0, fr:0, sa:0, }
On Thursday, June 21, 2012 8:57:28 AM UTC-7, Brad Karels wrote:
> I am new to mongo and not a JavaScript ninja so forgive my silliness. > That said, I am looking to perform a mapreduce on a set of events to get > counts by day of the week (i.e. What day of the week is most popular for > events?) My efforts have left me short around how to extract the day of > week (or month of year) from a date inside the mapReduce function. My > solution thus far looks as follows:
>> var day = value.date.getDay; // Here seems to be the sticky bit
>> if (day == 0) {
>> retVal.su += value.su;
>> }...{
>> } else {
>> retVal.sa += value.sa;
>> }
>> });
>> return retVal;
>> }
>> db.runCommand({
>> mapReduce: "track_event",
>> map: mapFunction,
>> reduce: reduceFunction,
>> out: "myOutput"
>> });
> I have been poking around here and other places a bit and have found date > operations like this seem to yet be a bit limiting. So if someone can put > me down a more correct path I'd appreciate any advice moving forward.
Thank you Scott and William - this adds clarity and got me over this hump!
I am still curious, however, as to why date.getDay() inside the reduce function returns "day of month" (e.g. 18 for 18-6-2012). To William's point, this should be unnecessary, but it's still bugging me a bit.
Thank you both for your input - I appreciate your help.
On Thursday, June 21, 2012 10:57:28 AM UTC-5, Brad Karels wrote:
> I am new to mongo and not a JavaScript ninja so forgive my silliness. > That said, I am looking to perform a mapreduce on a set of events to get > counts by day of the week (i.e. What day of the week is most popular for > events?) My efforts have left me short around how to extract the day of > week (or month of year) from a date inside the mapReduce function. My > solution thus far looks as follows:
>> var day = value.date.getDay; // Here seems to be the sticky bit
>> if (day == 0) {
>> retVal.su += value.su;
>> }...{
>> } else {
>> retVal.sa += value.sa;
>> }
>> });
>> return retVal;
>> }
>> db.runCommand({
>> mapReduce: "track_event",
>> map: mapFunction,
>> reduce: reduceFunction,
>> out: "myOutput"
>> });
> I have been poking around here and other places a bit and have found date > operations like this seem to yet be a bit limiting. So if someone can put > me down a more correct path I'd appreciate any advice moving forward.
