Daily Challenge #61 - Evolution Rate

Write a function getEvolutionRateMessage which takes two numbers before & after. The before value is the initial value of the evolution. The after value is the value after its evolution. An evolution can be calculated as follows:

evolution = (after - before) / before * 100

This function will return a string such that there are three possible outputs:
"A positive evolution of X%."
"A negative evolution of Y%."
"No evolution."

Examples:

getEvolutionRateMessage 11.29 45.79
getEvolutionRateMessage 95.12 66.84
getEvolutionRateMessage 0 27.35
getEvolutionRateMessage 41.26 0
getEvolutionRateMessage 1.26 1.26

"A positive evolution of 306%."
"A negative evolution of 30%."
"A positive evolution of 2735%."
"A negative evolution of 4126%."
"No evolution."

---

This challenge comes from aminnairi here on DEV. Want to propose a challenge idea for a future post? Email [e-mail] with your suggestions!

Comments

[Mat-R-Such]

python

def getEvolutionRateMessage(before,after):
    if before == 0 and after == 0:  return "No evolution."
    evolution = after * 100 if before == 0 else  before * 100 if after == 0 else round(((after-before) / before)*100)
    return "A positive evolution of "+str(int(evolution))+'%' if before<after else "A negative evolution of "+str(int(evolution*-1) if evolution <0 else int(evolution))+'%' if before > after else "No evolution."

[Anwar]

Since no one proposed a PHP solution, here I am!

if (!function_exists("getEvolutionRate")) {
    function getEvolutionRate(float $before, float $after): float {
        if ($before === 0.0) {
            return $after * 100;
        }

        if ($after === 0.0) {
            return -($before * 100);
        }

        return round(($after - $before) / $before * 100);
    }
}

if (!function_exists("getEvolutionRateMessage")) {
    function getEvolutionRateMessage(float $before, float $after): string {
        $evolutionRate = getEvolutionRate($before, $after);
        $evolutionRateToDisplay = abs($evolutionRate);
        $direction = $evolutionRate > 0 ? "positive" : "negative";

        return $evolutionRate === 0.0 ? "No evolution" : "A $direction evolution of $evolutionRateToDisplay%";
    }
}

getEvolutionRate() unit tests:

use PHPUnit\Framework\TestCase;

class GetEvolutionRateTest extends TestCase
{
    public function testShouldReturnPositiveRate()
    {
        $this->assertEquals(getEvolutionRate(11.29, 45.79), 306);
    }

    public function testShouldReturnOtherPositiveRate()
    {
        $this->assertEquals(getEvolutionRate(0, 27.35), 2735);
    }

    public function testShouldReturnNegativeRate()
    {
        $this->assertEquals(getEvolutionRate(95.12, 66.84), -30);
    }

    public function testShouldReturnOtherNegativeRate()
    {
        $this->assertEquals(getEvolutionRate(41.26, 0), -4126);
    }

    public function testShouldReturnZeroEvolution()
    {
        $this->assertEquals(getEvolutionRate(1.26, 1.26), 0);
    }
}

getEvolutionRateMessage() unit tests:

use PHPUnit\Framework\TestCase;

class GetEvolutionRateMessageTest extends TestCase
{
    public function testShouldReturnPositiveRateMessage()
    {
        $this->assertEquals(getEvolutionRateMessage(11.29, 45.79), "A positive evolution of 306%");
    }

    public function testShouldReturnOtherPositiveRateMessage()
    {
        $this->assertEquals(getEvolutionRateMessage(0, 27.35), "A positive evolution of 2735%");
    }

    public function testShouldReturnNegativeRateMessage()
    {
        $this->assertEquals(getEvolutionRateMessage(95.12, 66.84), "A negative evolution of 30%");
    }

    public function testShouldReturnOtherNegativeRateMessage()
    {
        $this->assertEquals(getEvolutionRateMessage(41.26, 0), "A negative evolution of 4126%");
    }

    public function testShouldReturnZeroEvolutionMessage()
    {
        $this->assertEquals(getEvolutionRateMessage(1.26, 1.26), "No evolution");
    }
}

[Amin]

I love those guards you are puting in your code. Really makes me want to go back and do PHP with you like the good ol'times!

[Anwar]

Let's do a side project together

[Avalander]

My knowledge of statistics is a bit rusty (yet I didn't use rust for this challenge), but I think that an increase from 0 to anything is basically an infinite rate and a decrease from anything to 0 is a negative 100% rate, so I disagree with the examples 3 and 4 and have written my solution accordingly.

Haskell, of course

get_rate :: Double -> Double -> String
get_rate before after
  | before == after = "No evolution."
  | before == 0     = "Infinite evolution."
  | evolution < 0   = "A negative evolution of " ++ (show' . abs) evolution ++ "%."
  | otherwise       = "A positive evolution of " ++ show' evolution ++ "%."
  where
    evolution = (after - before) * 100 / before
    show'     = show . round
    -- show_abs = show' . abs -- Hmm, maybe not the best name ever, let's leave it out.

Output

get_rate 11.29 45.79 -- "A positive evolution of 306%."
get_rate 95.12 66.84 -- "A negative evolution of 30%."
get_rate 0 27.35     -- "Infinite evolution."
get_rate 41.26 0     -- "A negative evolution of 100%."
get_rate 1.26 1.26   -- "No evolution."

[Dev Prakash]

def getEvolutionratemessage (before , after) :
    try :
        evolution = (after - before ) / before * 100 
    except ZeroDivisionError : 
        return "can't divide by zero " 

    if evolution > 0 :
        statement = f"A Positive evolution of {round(evolution)}%"
    elif evolution < 0:
        statement = f"A Negative evolution of {round(evolution)}%"
    else :
        statement = f"No evolution"
    return statement 

print (getEvolutionratemessage(95.12 , 66.84))

[Craig McIlwrath]

Haskell:

getEvolutionRateMessage :: Double -> Double -> String
getEvolutionRateMessage before after
  | evol > 0  = "A positive evolution of " ++ show evol ++ "%."
  | evol == 0 = "No evolution."
  | evol < 0  = "A negative evolution of " ++ show (0-evol) ++ "%." 
  where evol = (after - before) / before * 100

[Amin]

I long awaited this one. Haha!

[E. Choroba]

Perl solution. I still don't understand how the values are computed for zeroes, but it passes the tests :-)

#!/usr/bin/perl
use warnings;
use strict;
use feature qw{ say };

sub get_evolution_rate_message {
    my ($before, $after) = @_;
    return 'No evolution.' if $before == $after;
    return sprintf 'A %s evolution of %.0f%%.',
        qw(_ negative positive)[ $before <=> $after ],
        abs(($before - ($after || ($before+$before ** 2)))
            * 100 / ($before || 1))
}

use Test::More tests => 5;

is get_evolution_rate_message(11.29, 45.79), 'A positive evolution of 306%.';
is get_evolution_rate_message(95.12, 66.84), 'A negative evolution of 30%.';
is get_evolution_rate_message(0, 27.35),     'A positive evolution of 2735%.';
is get_evolution_rate_message(41.26, 0),     'A negative evolution of 4126%.';
is get_evolution_rate_message(1.26, 1.26),   'No evolution.';

[Amin]

Imagine that instead of going from 0 to 27.35, you are going from 0.0000000001 to 27.35. I think you'll have your answer here. 😉

[Cagatay Kaya]

Here is a Javascript arrow function, that uses nested ternary operators. Someone probably already posted this answer, but hey main point is that I took the challenge and solved by myself.

const getEvolutionRateMessage = (before, after) => {
  const rate = Math.round(
    (((after == 0 ? -before * before + before : after) - before) /
      (before == 0 ? 1 : before)) *
      100
  );
  return rate == 0
    ? "No evolution."
    : rate > 0
    ? `A positive evolution of ${rate}%.`
    : `A negative evolution of ${-1 * rate}%.`;
};

[Amin]

Thanks for showing us your solution. What's important is what you achieve at the end of the day!

[cvanpoelje]

My javascript solution :

const getEvolutionRateMessage = (before, after) => {
  evolution =
    before > 0 ? ((after - before) / before) * 100 : (after - before) * 100;
  return evolution === 0
    ? "No Evolution"
    : `A ${evolution > 0 ? "Positive" : "Negative"} evolution of ${Math.abs(
        evolution
      ).toFixed(2)}%`;
}

[Melvin Yeo]

I wrote it in Python, kept it as short as possible while maintaining clarity. 😎

def getEvolutionRateMessage(before, after):
    if before == after:
        return "No evolution"

    polarity = "positive" if after > before else "negative"
    evo_rate = round(abs(after - before) * 100 / (before if before != 0 and after != 0 else 1))

    return f"A {polarity} evolution of {evo_rate}%"

[Amin]

Neat! I like what they did with this new string interpolation thing in Python.

I Didn't know it was called a polarity. Learning new things every day. Yay!

[Dev Prakash]

{ % gist gist.github.com/devparkk/092171076... %}

[Melvin Yeo]

The code will throw an error if you pass in the following parameters
getEvolutionRateMessage 0 27.35 as you're dividing by 0.

[Dev Prakash]

Oyeeeeee
Thanks a lot , man
I appreciate it ...
Can u help me with how to publish my codes here in comment section ...
I don't really understand this markdown and all ...

[Amin]

Hi Prakash, you can refer to this link to see how code syntax highlighting works in markdown.

[Dev Prakash]

Thank you