How do I calculate julian dates from month-year data organized in columns

[bmac1]

Hi SAS community,

I have a data set of observations for different months in different years (spanning over 100 years), with the monthly  data arranged in 12 columns for each year as below:

Year       jan          feb         mar        apr         may       jun         jul           aug         sep         oct          nov        dec

1856       0.235     0.168     0.24        0.159     0.211     0.234     0.247     0.224     0.291     0.141     0.152     0.246

1857       0.231     -0.042    -0.058    0.024     -0.016    0.117     0.149     0.014     0.036     -0.117    -0.152    -0.266

1858       -0.204    -0.297    -0.054    0.228     0.106     -0.023    -0.144    -0.055    0.087     0.165     0.291     0.139

I want to convert the year-month data into a single long time series of julian dates, so that the observation of the first month in the first year (1856) gets assigned a julian date = 1856 + (0.5/12) = 1856.042, and so on.  The output file should have the new date variable in its own column, and the corresponding observation for that julian date, as below:

1856.041       0.235

1856.125       0.168

1856.208       0.24

...etc.

Has anyone some suggestions or code to do this (in SAS version 9)? 

Thanks for help.

[PaigeMiller]

/* UNTESTED CODE */
data want;
    set have;
    array x(*) jan--dec;
    do i=1 to dim(x);
        juldate = juldate(mdy(i,1,year));
        value=x(i);
        output;
     end;
     keep juldate value;
     format juldate julian7.;
run;

[bmac1]

Hi,
Thank you for a quick response - so much appreciated!
I just tried the code. However, I realize it is not quite what I had in mind...
I need to have the date as a decimal date (centred on the middle of each month) so not a real julian day. Sorry, I should have made that clearer in the first post. Every month (centred on the middle of the month so for example January would get a decimal value of 0.5/12 = 0.042) should be expressed as a fraction of the year, and accumulate during the year to a whole year, so the next year starts again with a decimal value. Like this...
1856

0.792

1856.792

1856

0.875

1856.875

1856

0.958

1856.958

1857

0.042

1857.042

1857

0.125

1857.125

1857

0.208

1857.208


Is there a way to create a decimal year value like this?

[ballardw]

For not standard values such as below, please indicate the actual date each is supposed to represent:

1856

0.792

1856.792

1856

0.875

1856.875

None of those resemble a Julian date in any form. Julian dates are YYDDD or YYYYDDD where Y is year and DDD is a 3-digit number of the day in a year.

I think you may also want to include some other months worked out just to make sure we understand how you are mangling month.

[bmac1]

Hi,

Thank you for replying. What I need is not really a julian date, but a decimal year date.  Sorry I did not make that clear enough in the original post.   In the meantime another community member has solved the question.  Please see the other posts in this thread for information.

[PaigeMiller · Accepted solution]

/* UNTESTED CODE */
data want;
    set have;
    array x(*) jan--dec;
    do i=1 to dim(x);
        juldate = year+(i-0.5)/12;
        value=x(i);
        output;
     end;
     keep juldate value;
run;

[bmac1]

Hi,



This worked perfectly! Thank you so much for your help.