How to remove the year from a datetime table column

I have a datetime table with

'01-Oct-2014'

'02-Oct-2014'

'03-Oct-2014'

'04-Oct-2014'

'05-Oct-2014'

and I would like to get the same table (or an additional column in that table) but with day-month only for each row

[Dyuman Joshi]

Simply change the format of the data -

%Data
y = datetime(["01-Oct-2014";
              "02-Oct-2014"
              "03-Oct-2014"
              "04-Oct-2014"
              "05-Oct-2014"])

y = 5×1 datetime array
   01-Oct-2014
   02-Oct-2014
   03-Oct-2014
   04-Oct-2014
   05-Oct-2014

%Change the format of the datetime array
y.Format = 'dd-MMM';

y

y = 5×1 datetime array
   01-Oct
   02-Oct
   03-Oct
   04-Oct
   05-Oct

[Paul Barrette]

Thanks @Dyuman Joshi. However, this code simply changes the formatting, but the underlying year data is still stored in the DATETIME object. What I'm trying to do is extract the day-month from each value.

[Dyuman Joshi]

Well, then you will have to get the day and the month data separately and store in a format you want to, as the datetime data type requires year as an input.

So, the question is how do you want store them?

[Star Strider]

The day and month functions exist.

[Dyuman Joshi]

Yes, I was going to provide that in my comment above, but thought that it would be better to answer after OP provides details on what the expected outcome is.

[Paul Barrette]

Sorry, I should have provided more info. I am plotting (with the 'scatter' command) five traces on the same graph, one per year (e.g., 2014 to 2018 inclusive). The horizontal axis for each year ranges from 01-Oct to 01-June (values for the vertical axis are from another matrix). But because the year is part of the object, these traces plot one after the other along that axis, not one on top of each other, which is what I'm looking for. To answer your question, I would store them as 'day-month' if only I could extract this from the current 'day-month-year' data.

ymd, as suggested earlier by @Star Strider, turns the datetime values into numeric arrays, but I'd like the 'day-month' label to appear on the horizontal axis of the graph.

[Dyuman Joshi]

How about this?

%Data
y = datetime(["01-Oct-2014";
              "02-Oct-2014"
              "03-Oct-2014"
              "04-Oct-2014"
              "05-Oct-2014"])

y = 5×1 datetime array
   01-Oct-2014
   02-Oct-2014
   03-Oct-2014
   04-Oct-2014
   05-Oct-2014

%Get the day
d = day(y)

d = 5×1

1 2 3 4 5

%Get the month, with the name in short form
m = month(y,'shortname')

m = 5×1 cell array
    {'Oct'}
    {'Oct'}
    {'Oct'}
    {'Oct'}
    {'Oct'}

%Single Quotation marks gives cell array
%Double Quotation marks gives string array
z = compose("%d-%s", d, string(m))

z = 5×1 string array
    "1-Oct"
    "2-Oct"
    "3-Oct"
    "4-Oct"
    "5-Oct"

Answer 1

[Star Strider]

The ymd function may be worth exploring.

EDIT — (18 Sep 2023 at 23:08)

Here is an example that also includes a scatter plot —

DT = datetime(['01-Oct-2014'
               '02-Oct-2014'
               '03-Oct-2014'
               '04-Oct-2014'
               '05-Oct-2018'
               '01-Oct-2018'
               '02-Oct-2018'
               '03-Oct-2018'
               '04-Oct-2018'
               '05-Oct-2018']);

T1 = table(DT,randn(size(DT))+[zeros(5,1);4*ones(5,1)])

T1 = 10×2 table
        DT           Var2   
    ___________    _________

    01-Oct-2014    -0.082131
    02-Oct-2014      0.47899
    03-Oct-2014      0.25127
    04-Oct-2014      0.99845
    05-Oct-2018      0.39241
    01-Oct-2018       4.2423
    02-Oct-2018       5.3109
    03-Oct-2018       4.1244
    04-Oct-2018       3.8779
    05-Oct-2018        4.609

[y,m,d] = ymd(DT);                                              % Date Components
ix = findgroups(m, d);                                          % Indices Of Months & Days

scattery = accumarray(ix, T1{:,2}, [], @(x){x});                % Accumulate 'Var2' Values By Day & Month
mc = month(DT,'shortname');

% compose('%s-%02d',string(mc),day(DT))
x = unique(compose('%s-%02d',string(mc),day(DT)),'stable');
dtx = datetime(x,'InputFormat','MMM-dd');
y = cell2mat(scattery.');                                       % Convert Cell Array To Numeric Array & Transpose

figure
scatter(dtx, y(1,:), 's', 'filled', 'DisplayName','2014')
hold on
scatter(dtx, y(2,:), 's', 'filled', 'DisplayName','2018')
hold off
grid
legend('Location','best')

I am not certain what you want to do.

.

[Paul Barrette]

This works - thanks @Star Strider. Though this is intricate coding for me (an opportunity the learn!). I did try the solution offered by @Dyuman Joshi, much simpler, but I could not make it work.

[Star Strider]

As always, my pleasure!