Kotlin + Maths

Grab your notebook cause in this talk, we are gonna talk about Math and Kotlin! Especially in the power that Kotlin has to run long operations and the power to perform some calculations like computing min, max, an average of numbers stored in a list! - from sumOf {} to multi-dimensional arrays to charts!

Transcript

1. Kotlin + Maths
   Dinorah Tovar @ddinorahtovar
   
   Google Developer Expert - Android
   Santo Domingo
   

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2. Disclaimer - I’m
   not a data science
   engineer
   

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3. Left Aligned Title
   Kotlin help us to solve many problems - but specially in maths!
   Math’s are coolest thing!
   • A fast operational language
   • Mathematical expressions
   • Algebraic data types (sealed class)
   • We can do simple functions - from basic to complex
   

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4. Simple quote or
   statement goes
   here. Ideally limit
   to four or five
   lines max.
   This function takes
   mseconds
   258
   fun main() {
   
   
   val y = complex(2, 1)
   
   
   var x = complex(0, 0)
   
   
   val time = measureTimeMillis {
   
   
   repeat(10000000) {
   
   
   x += y
   
   
   x *= y
   
   
   x -= y
   
   
   x /= y
   
   
   }
   
   
   }
   
   
   }
   

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5. Simple quote or
   statement goes
   here. Ideally limit
   to four or five
   lines max.
   This function takes
   seconds
   2.76
   def main():
   
   
   z = complex(2, 1)
   
   
   w = complex(0, 0)
   
   
   start = time.time()
   
   
   for i in range(0, 10000000):
   
   
   w += z
   
   
   w *= z
   
   
   w -= z
   
   
   w /= z
   
   
   ende = time.time()
   

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6. 9 times
   At least
   more efficient
   

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7. Mathematical expressions are pretty much
   pseudocode
   

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8. Left Aligned Title
   2x + 10
   First degree
   equation
   fun calc(x: Int) : Int {
   
   
   return 2*x + 10
   
   
   }
   

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9. Left Aligned Title
   10
   ∑
   i=1
   1
   i + 1
   Summation
   val sum = 0
   
   
   for (i in 1..10) {
   
   
   sum += 1/(i+1)
   
   
   }
   fun f() =
   
   
   (1..10).map { i ->
   
   
   1 / (i + 1)
   
   
   }.sum()
   

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10. Left Aligned Title
    3
    ∏
    i=1
    i
    Product
    fun f() =
    
    
    (1..3).fold(
    
    
    1L, Long::times)
    

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11. ADT is a type which is represented by
    several other subtypes
    

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12. Simple quote or
    statement goes
    here. Ideally limit
    to four or five
    lines max.
    ADT are only
    Class
    Sealed
    sealed class Tree
    
    
    data class Node(
    
    
    val value: T,
    
    
    val left: Tree = Empty,
    
    
    val right: Tree = Empty
    
    
    ) : Tree()
    

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13. Simple quote or
    statement goes
    here. Ideally limit
    to four or five
    lines max.
    ADT can create
    Sequences
    Nodes
    fun f() {
    
    
    val tree = Node(
    
    
    10,
    
    
    20,
    
    
    Node(40, 20, 10)
    
    
    )
    
    
    // we can create ext function
    
    
    // and get the result
    
    
    }
    

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14. Algebraic operations
    

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15. Left Aligned Title
    {1,2,4,10}
    Average
    
    
    Max - Min
    fun f() {
    
    
    val seq = floatArrayOf(
    
    
    1F,
    
    
    2F,
    
    
    4F,
    
    
    10F
    
    
    )
    
    
    val avg = seq.average()
    
    
    val max = seq.max()
    
    
    val min = seq.min()
    
    
    }
    

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16. Left Aligned Title
    (
    222
    222
    222
    )
    Multi-
    dimensional
    Vectors
    fun f() {
    
    
    val mx = arrayOf(
    
    
    arrayOf(floatArrayOf(2F, 2F, 2F)),
    
    
    arrayOf(floatArrayOf(2F, 2F, 2F)),
    
    
    arrayOf(floatArrayOf(2F, 2F, 2F))
    
    
    )
    
    
    val normArray = mx.map {
    
    
    column -> column.map {
    
    
    row -> row.map { element ->
    
    
    element / 255F
    
    
    }
    
    
    }
    
    
    }
    
    
    }
    

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17. Probability and Statistics
    

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18. Let’s solve a problem
    Let’s calculate the probability of
    the weather in the last week in
    Mexico City!
    Last week weather
    Partially Sunny
    Rainy
    Rainy
    Cloudy
    Partially Sunny
    

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19. Just rainy probability
    val weatherMexicoCity = arrayOf(
    
    
    "Partially Sunny",
    
    
    "Rainy" ,
    
    
    "Partially Sunny" ,
    
    
    "Cloudy",
    
    
    "Rainy"
    
    
    )
    val rainyProbability = weatherMexicoCity.count { it == "Rainy" } /
    weatherMexicoCity.size
    

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20. How about all the weathers
    val weatherMexicoCity = arrayOf(
    
    
    "Partially Sunny",
    
    
    "Rainy" ,
    
    
    "Partially Sunny" ,
    
    
    "Cloudy",
    
    
    "Rainy"
    
    
    )
    val generalProbability = weatherMexicoCity.map {
    
    
    label -> labels.count { it == label } / labels.size
    
    
    }
    

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21. Charts + Statistics
    

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22. Kotlin has integration for Notebooks -
    specifically for Jupiter
    

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24. Kotlin + Maths
    Dinorah Tovar @ddinorahtovar
    
    Google Developer Expert - Android
    Santo Domingo
    

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