How to remove the year from a datetime table column

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0 个投票

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

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Paul Barrette 2023-9-18

移动：Dyuman Joshi 2023-9-20

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 2023-9-18

移动：Dyuman Joshi 2023-9-20

在 MATLAB Online 中打开

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"

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Answer 1

Star Strider 2023-9-18

编辑：Star Strider 2023-9-18

在 MATLAB Online 中打开

0 个投票

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.

.

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Paul Barrette 2023-9-20

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 2023-9-20

As always, my pleasure!

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How to remove the year from a datetime table column

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