Convert Number of Days to just a number

I'm doing a lot of operations on day and time for some solar position calculations. In doing so I have a decimal day value which is a day + a duration (ex. 328.32 days).

I need to use this value in calculations and as inputs to trig functions in degrees- but in trig functions I get:

Check for incorrect argument data type or missing argument in call to function 'sind'.

Error in AngleSimulation (line 27)

EoT = 9.87*sind(2*B) - 7.53*cosd(B) - 1.5*sind(B);

I am trying to convert the day value to just a number so I can use it in those equations.

Code here- relevant variable is "d"

%%inputs

date = "24/11/2023"; %DD/mm/yyyy

time = "14:43"; %'hh:mm' from 00:00-24:00

timezonedif = "-07:00"; %"+-00:00 from UTC"

long = -105.944183;%degrees East or - degrees West

lat = 35.691544;%degrees North or - degrees south

%%converting inputs

date = datetime(date, "InputFormat","dd/MM/uuuu");

time = duration(time, 'InputFormat', 'hh:mm', 'Format', 'h');

timezonedif = duration(timezonedif, 'InputFormat', 'hh:mm');

UTCtime = time + timezonedif;

UTCtimedayfrac = duration(UTCtime, 'Format', 'd');

%%finding day

d = day(date, "dayofyear") + (UTCtimedayfrac);

%%finding hour angle

%local standard time meridian

LSTM = 15 * UTCtime; %degrees

%equation of time

B = 360/365*(d - 81);%degrees

EoT = 9.87*sind(2*B) - 7.53*cosd(B) - 1.5*sind(B);

%time correction factor

TC = 4*(long - LSTM) + EoT;

%local solar time

LST = time + TC/60

%hour angle

Answer 1

[Star Strider]

As it currently exists, ‘B’ is a duration.

Use the days function to convert it to a double-precision number.

Then, it works —

date = "24/11/2023"; %DD/mm/yyyy
    
time = "14:43"; %'hh:mm' from 00:00-24:00

date = datetime(date, "InputFormat","dd/MM/uuuu");
time = duration(time, 'InputFormat', 'hh:mm', 'Format', 'h');

timezonedif = "-07:00"; %"+-00:00 from UTC"
timezonedif = duration(timezonedif, 'InputFormat', 'hh:mm');
UTCtime = time + timezonedif;
UTCtimedayfrac = duration(UTCtime, 'Format', 'd');
d = day(date, "dayofyear") + (UTCtimedayfrac);
B = 360/365*(d - 81) %degrees

B = duration
   243.93 days

whos B

  Name      Size            Bytes  Class       Attributes

  B         1x1                10  duration              

B = days(B)

B = 243.9336

whos B

  Name      Size            Bytes  Class     Attributes

  B         1x1                 8  double              

EoT = 9.87*sind(2*B) - 7.53*cosd(B) - 1.5*sind(B)

EoT = 12.4479

.

[Nathan Liscouski]

That works great, Thank you!!

[Star Strider]

As always, my pleasure!