How can I list individual year from the datetime table?

Hi all,

I have a datetime matrix (2003 to 2019, 17 years) and I want to list the range of index for individual years. For example, a cell array named "YearList" that has 17 cells and each of them will contain the date list of individual year. So, all the dates from 2003 will be in the first cell of the array and so on.

I have attached the .mat file. Any feedback will be greatly appreciated!!

[Walter Roberson]

See https://www.mathworks.com/matlabcentral/answers/1940499-how-to-get-the-indices-based-on-month-and-year#answer_1207779 but you would only need the y output of ymd

Answer 1

[Dave B]

The splitapply function makes this pretty easy - here the idea is to split the data by year, and then apply a function that turns a chunk of data into a cell. This approach has the downside (or upside) of only including years that are in your dataset (so 16 cells, because there's no data from 2004).

load("DateList.mat")
YearList=splitapply(@(x){x},Per,findgroups(Per.Year))

YearList = 16×1 cell array
    {12348×1 datetime}
    {15497×1 datetime}
    {16128×1 datetime}
    {15360×1 datetime}
    {16128×1 datetime}
    {14688×1 datetime}
    {15168×1 datetime}
    {15456×1 datetime}
    {15744×1 datetime}
    {16896×1 datetime}
    {16224×1 datetime}
    {15456×1 datetime}
    {15552×1 datetime}
    {16800×1 datetime}
    {15456×1 datetime}
    {17760×1 datetime}

[Ashfaq Ahmed]

Thank you so much!!

Answer 2

[Peter Perkins]

I'm gonna go Dave one better:

>> load DateList.mat
>> t = table(Per);
>> t.Year = year(t.Per);
>> t2 = varfun(@(x){x},t,InputVariables="Per",GroupingVariable="Year",OutputFormat="table")
t2 =
  16×3 table
    Year    GroupCount         Fun_Per      
    ____    __________    __________________
    2003      12348       {12348×1 datetime}
    2005      15497       {15497×1 datetime}
    2006      16128       {16128×1 datetime}
    2007      15360       {15360×1 datetime}
    2008      16128       {16128×1 datetime}
    2009      14688       {14688×1 datetime}
    2010      15168       {15168×1 datetime}
    2011      15456       {15456×1 datetime}
    2012      15744       {15744×1 datetime}
    2013      16896       {16896×1 datetime}
    2014      16224       {16224×1 datetime}
    2015      15456       {15456×1 datetime}
    2016      15552       {15552×1 datetime}
    2017      16800       {16800×1 datetime}
    2018      15456       {15456×1 datetime}
    2019      17760       {17760×1 datetime}