Computing Zodiac Signs from Dates

Computing Zodiac Signs from Dates#

In this article, we will describe how to approximate the computation of zodiac signs based on given numerical inputs representing a month and a day. The data for zodiac signs and their corresponding date ranges is typically presented in a tabular format, which can be a bit challenging for machine processing. Therefore, we will take steps to clean, organize, and utilize this data efficiently.

Introduction#

The initial problem is to handle a table layout that is suitable for human consumption but is not optimal for computation. The table generally consists of four columns, but essentially it only represents two key columns: the zodiac sign and the date range. While the date ranges are formatted for readability, they can be cumbersome for computational needs.

To start with, we can create a representation of zodiac signs and their date ranges in APL:

⍝ Zodiac signs and corresponding date ranges
r ← 6 4 ⍴ 'Aries ' 'March 21–April 19 ' 'Libra ' 'September 23–October 22' 
           'Taurus ' 'April 20–May 20 ' 'Scorpio ' 'October 23–November 21' 
           'Gemini ' 'May 21–June 20 ' 'Sagittarius ' 'November 22–December 21' 
           'Cancer ' 'June 21–July 22 ' 'Capricorn ' 'December 22–January 19' 
           'Leo ' 'July 23–August 22 ' 'Aquarius ' 'January 20–February 18' 
           'Virgo ' 'August 23–September 22 ' 'Pisces ' 'February 19–March 20'

Cleaning the Data#

Column Permutation#

To begin, we need to group the relevant columns properly. The first and third columns should be paired, and likewise for the second and fourth columns. Thus, we need to permute the columns to get a more manageable structure.

⍝ Permuting columns
r[;1 3 2 4]

This expression rearranges the columns to better align the zodiac signs with their date ranges.

Data Transposition#

Next, we will transpose the table. This transposition will allow us to have all the zodiac signs in one row, followed by all the date ranges in another, simplifying our data.

⍝ Transposing the table
⍉r[;1 3 2 4]

Table Rotation#

Another challenge arises due to the fact that this table starts from March 21st, while the Gregorian calendar begins in January. To rectify this, we will perform a negative two-step horizontal rotation to start with January instead.

⍝ Rotating the table
¯2⌽2 12 ⍴ ⍉r[;1 3 2 4]

This transformation allows us to present zodiac signs beginning with Capricorn.

Splitting the Table#

After rotation, we can split the table into two vectors: one for the zodiac signs (s) and another for the date ranges (d). Upon inspection, we realize that the zodiac signs contain unwanted trailing spaces, which we need to remove.

Removing Spaces#

We can utilize a set difference approach to eliminate spaces from our zodiac signs vector. A modified assignment can be employed here, allowing us to directly update the vector without creating a new variable.

⍝ Removing spaces from zodiac signs
s ~¨ ' '

Date Parsing#

Next, we will parse the dates. Knowing that there is a unique month for each zodiac sign, we will focus on extracting the day of the month. We will take the first number in each date range, as the last day of one sign is the day before the first day of the next sign.

Using Quad VFI#

To simplify the parsing, we leverage the quad vfi function to verify that tokens are proper numbers and convert them accordingly. By specifying suitable field separators, we can accurately extract the day information.

⍝ Using quad VFI to parse dates
⍳12
⍝ Structure for days of the month for each zodiac sign
c ← (⍳12), ⍪ {2 2⊃ ' –' ⎕VFI ⍵}¨d

Creating a Cutoff Table#

Using the parsed day values, we can create a lookup table for cutoff dates, associating each zodiac sign with its corresponding starting date.

Finding Zodiac Signs#

Next, we need to determine the zodiac sign associated with a given date. It is important to note that certain dates at the beginning of the year (before January 20) also correspond to Capricorn.

One way to represent this cyclic nature is by using a modular approach. We can rotate the list of zodiac signs, ensuring Capricorn is first and adjusting our indices to reflect the cutoff dates accurately.

Interval Index#

To facilitate lookup operations, we implement an interval index that relates specific date ranges to their corresponding zodiac signs. This index will help us determine which zodiac sign matches any given date.

Final Function#

Finally, we will encapsulate all of the above logic into a standalone function. This function can accept a date as an argument and return the corresponding zodiac sign based on its computations.

# Example function (pseudo-code)
def get_zodiac_sign(month, day):
    # Implement the logic as described above
    pass

Conclusion#

We have developed a structured approach to compute zodiac signs from given dates. By cleaning and organizing the data, implementing proper transformation and parsing techniques, we can achieve efficient computation.

Thank you for following along and happy coding!

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