# Error in datetime array format for writing new matrix

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Anak Agung Adhi Dermawan on 14 Sep 2022
Edited: Stephen23 on 15 Sep 2022
Hello matlab expert, I have this timeseries data in txt format. the first column contain year data in year decimal format. I want to convert the year decimal format into datetime and save it as new txt file but I got an error in writematrix because the datetime format. what function should I use?
clc;clear; close all;
format long g
filename1 = 'C:\ZTD\PWVctul.txt';
data1 = readmatrix(filename1);
T1 = array2table(data1);
tt = table2timetable(T1, 'RowTimes',datetime(0,1,1) + years(data1(:,1)));
tt4 = timetable2table (tt);
pw = table2array (tt4(1:end,"data12"));
time = table2array (tt4(1:end,"Time"));
newdata = [ty pw];
writematrix (newdata,'PWVctuldatetime.txt','Delimiter','space');
##### 4 CommentsShowHide 3 older comments
Stephen23 on 14 Sep 2022
Edited: Stephen23 on 14 Sep 2022
"Seems like a reasonable enhancement to the conversion types in datetime to build into it."
I asked about this on another thread, got this response:

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### Accepted Answer

Stephen23 on 14 Sep 2022
Edited: Stephen23 on 14 Sep 2022
Ah, fractional years. Here is one way to convert a fractional year (yes, even leap years) to datetime:
format long G
M = readmatrix('PWVctul.txt')
M = 1831×2
1.0e+00 * 2014.99980974125 0.0627371458432432 2015.00236052519 0.0619196013484259 2015.00509549932 0.0583826355657704 2015.00783049723 0.0549544140538488 2015.01057022325 0.0497257245907533 2015.01330994928 0.0412166574719457 2015.01604967531 0.0460983177325905 2015.01878464955 0.0448768178251868 2015.02151964734 0.0450682606219937 2015.02425937337 0.0464028118802565
X = M(:,2); % data
Y = M(:,1); % year
Z = datetime(floor(Y),1,1,'Format','y/MM/dd HH:mm:ss.SSSSSSSSS');
Z = Z + mod(Y,1).*((Z+calyears(1))-Z)
Z = 1831×1 datetime array
2014/12/31 22:20:00.000057449 2015/01/01 20:40:41.522390028 2015/01/02 20:38:11.666557966 2015/01/03 20:35:42.560648069 2015/01/04 20:35:42.560410186 2015/01/05 20:35:42.560494974 2015/01/06 20:35:42.560572592 2015/01/07 20:33:12.708211031 2015/01/08 20:30:43.598515132 2015/01/09 20:30:43.598592750 2015/01/10 20:30:43.598677538 2015/01/11 20:30:43.598762327 2015/01/12 20:30:43.598524444 2015/01/13 20:28:13.749941713 2015/01/14 20:25:44.636782485 2015/01/15 20:25:44.636544602 2015/01/16 20:25:44.636629390 2015/01/17 20:25:44.636714179 2015/01/18 20:23:14.791594778 2015/01/19 20:20:45.674649549 2015/01/20 20:20:45.674734337 2015/01/21 20:20:45.674811954 2015/01/22 20:20:45.674896743 2015/01/23 20:18:15.833247843 2015/01/24 20:15:46.712832112 2015/01/25 20:15:46.712916901 2015/01/26 20:15:46.712686189 2015/01/27 20:15:46.712763806 2015/01/28 20:13:16.874900907 2015/01/29 20:10:47.751014676
T = table(Z,X)
T = 1831×2 table
Z X _____________________________ __________________ 2014/12/31 22:20:00.000057449 0.0627371458432432 2015/01/01 20:40:41.522390028 0.0619196013484259 2015/01/02 20:38:11.666557966 0.0583826355657704 2015/01/03 20:35:42.560648069 0.0549544140538488 2015/01/04 20:35:42.560410186 0.0497257245907533 2015/01/05 20:35:42.560494974 0.0412166574719457 2015/01/06 20:35:42.560572592 0.0460983177325905 2015/01/07 20:33:12.708211031 0.0448768178251868 2015/01/08 20:30:43.598515132 0.0450682606219937 2015/01/09 20:30:43.598592750 0.0464028118802565 2015/01/10 20:30:43.598677538 0.0451572386581995 2015/01/11 20:30:43.598762327 0.0523973221610946 2015/01/12 20:30:43.598524444 0.0631753909682948 2015/01/13 20:28:13.749941713 0.0593898128672308 2015/01/14 20:25:44.636782485 0.0557321130217992 2015/01/15 20:25:44.636544602 0.0555264085669299
writetable(T,'newfile.txt') % no problem
##### 2 CommentsShowHide 1 older comment
Stephen23 on 14 Sep 2022
Another approach to converting from decimal years to datetime:
format long G
M = readmatrix('PWVctul.txt');
Y = M(:,1); % year
Z = datetime(floor(Y)+[0,1],1,1,'Format','y/MM/dd HH:mm:ss.SSSSSSSSS');
Z = Z(:,1) + mod(Y,1).*diff(Z,1,2)
Z = 1831×1 datetime array
2014/12/31 22:20:00.000057449 2015/01/01 20:40:41.522390028 2015/01/02 20:38:11.666557966 2015/01/03 20:35:42.560648069 2015/01/04 20:35:42.560410186 2015/01/05 20:35:42.560494974 2015/01/06 20:35:42.560572592 2015/01/07 20:33:12.708211031 2015/01/08 20:30:43.598515132 2015/01/09 20:30:43.598592750 2015/01/10 20:30:43.598677538 2015/01/11 20:30:43.598762327 2015/01/12 20:30:43.598524444 2015/01/13 20:28:13.749941713 2015/01/14 20:25:44.636782485 2015/01/15 20:25:44.636544602 2015/01/16 20:25:44.636629390 2015/01/17 20:25:44.636714179 2015/01/18 20:23:14.791594778 2015/01/19 20:20:45.674649549 2015/01/20 20:20:45.674734337 2015/01/21 20:20:45.674811954 2015/01/22 20:20:45.674896743 2015/01/23 20:18:15.833247843 2015/01/24 20:15:46.712832112 2015/01/25 20:15:46.712916901 2015/01/26 20:15:46.712686189 2015/01/27 20:15:46.712763806 2015/01/28 20:13:16.874900907 2015/01/29 20:10:47.751014676
... etc.

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