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Julian Day Number: Algorithm and Calculation, Slides of Computer Science

Biju Patnaik University of TechnologyComputer Science

Information on the julian day number, its definition, algorithm, and code structure for a programming project. Students will learn how to calculate julian day numbers using a thirteen-step algorithm and write functions to input data and calculate the numbers. The document also covers data validation and the use of stubs during program development.

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Project one March 30, 2006
1
First Project
First Project –
–Julian Day
Julian Day
Number Calculation
Number Calculation
Larry Caretto
Computer Science 106
Computing in Engineering and
Science
March 30, 2006
2
Outline
• Outline first project
– Goals of project
– Connection with exercise seven
• Julian day number
– Definition
– Algorithm
• Code structure for first project
3
Project One Goals
• Design a program with several functions
• Look at communication among several
functions in a single program
• Write routine using mathematical
statements (and choice statements)
from pseudocode
• See that functions developed in a
general purpose manner for one code
can be reused in another code
4
What is a Julian Day Number?
• Continuous time used by astronomers
• Integer part is number of days
• Decimal part is fraction of a day starting
at noon: 6 pm is 0.25; midnight is 0.5
• Class start time,12:30 pm on Tuesday,
March 28, 2006 was Julian date number
2453823.02083333
– Fractional part is fractional part of a day
starting at noon (1/48 = 0.02083333…)
– What is JDN for start of today’s class?
2453825.02083333
5
Julian Day Number Cases
2454102.499998811:59:59.9 pm1-Jan-2007
2454102noon1-Jan-2007
2454101.50:00:00 am1-Jan-2007
2454101.256:00:00 pm31-Dec-2006
Julian NumberTimeCalendar Date
Your program must match these results!
• Run sample cases shown in assignment
6
Julian Day Number Algorithm
• Thirteen-step algorithm in exercise notes
– requires user input of integer year, month,
day, hour (0-23), minutes
• Use type double for seconds
– use integer operations on month, day, year
• To get fraction of day convert time to
common elapsed time (hours, minutes or
seconds) and divide by 24 h = 1440 min =
86,400 s
• Convert types to double before division!
pf3
pf4

Partial preview of the text

Download Julian Day Number: Algorithm and Calculation and more Slides Computer Science in PDF only on Docsity!

First ProjectFirst Project – – Julian DayJulian Day

Number CalculationNumber Calculation

Larry Caretto Computer Science 106

Computing in Engineering and

Science

March 30, 2006

2

Outline

  • Outline first project
    • Goals of project
    • Connection with exercise seven
  • Julian day number
    • Definition
    • Algorithm
  • Code structure for first project

3

Project One Goals

  • Design a program with several functions
  • Look at communication among several

functions in a single program

  • Write routine using mathematical

statements (and choice statements)

from pseudocode

  • See that functions developed in a

general purpose manner for one code

can be reused in another code

4

What is a Julian Day Number?

  • Continuous time used by astronomers
  • Integer part is number of days
  • Decimal part is fraction of a day starting

at noon: 6 pm is 0.25; midnight is 0.

  • Class start time,12:30 pm on Tuesday,

March 28, 2006 was Julian date number

  • Fractional part is fractional part of a day starting at noon (1/48 = 0.02083333…)
  • What is JDN for start of today’s class?

5

Julian Day Number Cases

1-Jan-2007 11:59:59.9 pm 2454102.

1-Jan-2007 noon 2454102

1-Jan-2007 0:00:00 am 2454101.

31-Dec-2006 6:00:00 pm 2454101.

Calendar Date Time Julian Number

Your program must match these results!

  • Run sample cases shown in assignment

6

Julian Day Number Algorithm

  • Thirteen-step algorithm in exercise notes
    • requires user input of integer year, month, day, hour (0-23), minutes - Use type double for seconds
    • use integer operations on month, day, year
  • To get fraction of day convert time to

common elapsed time (hours, minutes or

seconds) and divide by 24 h = 1440 min =

86,400 s

  • Convert types to double before division!

7

Typical Algorithm Steps

  • Subtract 14 from the month and divide

the result by 12. Discard the remainder.

Call the quotient J.

  • Define K as J plus 4800 plus the year.
  • Multiply K by 1461 and divide the result

by 4. Discard the fractional part and call

the quotient L.

  • And a few more steps like these

8

Project One Code

  • Use data validation functions from

exercise seven

  • getValidInt
  • getMaxDays
  • leap
  • Write main, input and Julian Day functions
  • Use getValidDouble and getDoubleGELT

functions from project one assignment

  • Write three other functions (or stubs)

similar to getDoubleGELT

9

Main Function for Project One

  • Use outer loop for repeated input of

different cases (see task three of

exercise one for general structure)

  • Many did this for exercises five and six
  • Within this loop
  • Call input function for data on year, month, day, hour, minute second
  • Pass input information to function that calculates Julian Day Number
  • Print input and Julian Day Number
  • Use setprecision to match test cases 10

Input Data Function

  • Uses getValidInt and getValidDouble
  • Code is extension of input function from

task two of exercise seven

  • Must use pass by reference to return

variables to main function

  • Possible prototype void getInput( int& month, int& day, int& year, int& hour, int& minute, double& second);

11

Valid double Input

  • For valid integer input we can have

input equal to max and min values

  • For real input we want to have choices
    • User input less than or less-than-or-equal- to a stated maximum value
    • User input greater than or greater-than-or- equal-to a stated minimum value
  • User calls getValidDouble function

that specifies choices for both maximum

and minimum values

12

getValidDouble

  • This function returns a value for a type double

variable that is with a range set by the user

  • The user can also specify if variable is > or >=

the minimum value

  • Similarly it is possible to specify that the

variable is < or <= the maximum value

  • The specifications of the lower and upper limit

are done by the use of strings

  • “<“ or “<=“ specify the kind of upper limit
  • “>” or “>=“ specify the kind of lower limit

19

Project One Summary

  • Functions from

exercise seven or

given in notes

  • getValidInt
  • getValidDouble
  • getDoubleGELT
  • getMaxDays
  • leap
  • Uses the following eleven functions
  • New
  • main
  • Input data function
  • Julian Day Number calculation
  • Three functions similar to getDoubleGELT (or stubs) 20

Lab Quiz April 4

  • One hour, open book and notes
  • No help from instruction except in

extreme cases of computer problems

  • Do as much work as possible on simple

programming assignment

  • Will have answers that must be matched
  • Will include choice statements, looping,

and reading data from a file

  • Some sample questions in March 16

lecture presentation

21

Sample Quiz Problem

  • Ask a user for input of two numbers
  • Compute the sum of all even numbers

in the range input by the user, including

the user input values

  • E. g. if the user inputs 6 1 your program should compute 2 + 4 + 6 = 12
  • Watch out for larger number as first input and input of odd numbers as either start or finish

22

Solution

int first, last, i, sum = 0; cin << first << last; if ( first > last ) { int temp = first; first = last; last = temp; } if ( first % 2 != 0 ) first++; for ( i = first; i <= last; i += 2 ) sum += i;

  • Makes sure first

number in sum

is even

  • What about last

number?

23

Question about Solution

if ( first % 2 != 0 ) first++; for ( i = first; i <= last; i += 2 ) sum += i;

  • The first statement assures that the initial

number in the sum is even

  • What about the last number?
    • If last is even, the i <= last continuation condition will include it in the sum
    • If last is odd the condition will include the last even number ( i <= 7 includes 6, not 8) 24

Real Sample Quiz Problem

  • Actual problem would be to repeat the

sample code repeatedly until user

enters 0 0 for first and last

cin << first << last; while ( first != 0 && last != 0 ) { // place code for a single // calculation here cin << first << last; }