finance

4 files changed, 140 insertions, 0 deletions

diff --git a/finance/equal_principal.py b/finance/equal_principal.py
new file mode 100644
index 0000000..97af5d2
--- /dev/null
+++ b/finance/equal_principal.py
@@ -0,0 +1,17 @@
+
+
+def monthly_analysis(p, r, n):
+    r /= 12
+    paied_p = 0
+    for i in range(n):
+        month_pay = p/n + (p - paied_p)*r
+        print(i, month_pay, p/n, (p-paied_p)*r)
+        paied_p += p/n
+
+
+if __name__ == '__main__':
+
+    p = 2000000
+    r = 0.055
+    n = 30*12
+    monthly_analysis(p, r, n)
diff --git a/finance/equal_principal_interest.py b/finance/equal_principal_interest.py
new file mode 100644
index 0000000..035fd8c
--- /dev/null
+++ b/finance/equal_principal_interest.py
@@ -0,0 +1,19 @@
+
+
+def monthly_analysis(p, r, n):
+    r = r/12
+    month_p_and_i = p*r*(1+r)**n/((1+r)**n - 1)
+    remaining_p = p
+    for i in range(n):
+        month_i = remaining_p*r
+        month_p = month_p_and_i - month_i
+        remaining_p -= month_p
+        print(i, month_p_and_i, month_p, month_i)
+
+
+if __name__ == '__main__':
+    p = 600000
+    r = 0.06
+    n = 20*12
+    monthly_analysis(p, r, n)
+
diff --git a/numerical/image_inter.py b/numerical/image_inter.py
new file mode 100644
index 0000000..97b37d9
--- /dev/null
+++ b/numerical/image_inter.py
@@ -0,0 +1,93 @@
+'''
+    use bilinear interpolation to resize an image
+    https://www.brezeale.com/?p=812
+'''
+
+import numpy as np
+from PIL import Image
+
+
+def resizeImage(name):
+    img1 = Image.open(name)
+
+    old = np.asarray(img1)  # convert to Numpy array
+    rows, cols, layers = old.shape
+    new = np.zeros((2 * rows - 1, 2 * cols - 1, layers))
+    print("original dimensions:", old.shape)
+
+    for layer in range(3):
+        new[:, :, layer] = resizeLayer(old[:, :, layer])
+
+    # convert the values to unsigned, 8-bit integers
+    new = new.astype(np.uint8)
+    print("     new dimensions:", new.shape)
+
+    img2 = Image.fromarray(new)  # convert back to Image
+    newName = "big-" + name
+    img2.save(newName)
+
+
+def resizeLayer(old):
+    rows, cols = old.shape
+
+    rNew = 2 * rows - 1
+    cNew = 2 * cols - 1
+    new = np.zeros((rNew, cNew))
+
+    # move old points
+    new[0:rNew:2, 0:cNew:2] = old[0:rows, 0:cols]
+
+    ''' alternative approach
+    # something like this would be necessary in languages
+    #   that don't support slicing
+    new = np.zeros( (2*rows - 1, 2*cols - 1) )
+    for r in range(rows) :
+        for c in range(cols) :
+            new[2*r, 2*c] = old[r,c]
+
+    rows, cols = new.shape
+    '''
+
+    # produce vertical values
+    new[1:rNew:2, :] = (new[0:rNew - 1:2, :] + new[2:rNew:2, :]) / 2
+    ''' alternative approach
+    for r in range(1, rows, 2) :
+        for c in range(0, cols, 2) :
+            # top + bottom
+            new[r,c] = ( new[r-1,c] + new[r+1,c] ) // 2
+    '''
+
+    # produce horizontal values
+    new[:, 1:cNew:2] = (new[:, 0:cNew - 1:2] + new[:, 2:cNew:2]) / 2
+    ''' alternative approach
+    for r in range(0, rows, 2) :
+        for c in range(1, cols, 2) :
+            # left + right
+            new[r,c] = ( new[r,c-1] + new[r,c+1] ) // 2
+    '''
+
+    # produce center values
+    new[1:rNew:2, 1:cNew:2] = (new[0:rNew - 2:2, 0:cNew - 2:2] +
+                               new[0:rNew - 2:2, 2:cNew:2] +
+                               new[2:rNew:2, 0:cNew - 2:2] +
+                               new[2:rNew:2, 2:cNew:2]) / 4
+    ''' alternative approach
+    for r in range(1, rows, 2) :
+        for c in range(1, cols, 2) :
+            # top + bottom + left + right
+            new[r,c] = ( new[r-1,c] + new[r+1,c] + new[r,c-1] + new[r,c+1] ) // 4
+    '''
+
+    return new
+
+
+####################  main  ####################
+
+test = np.array([[10, 40], [30, 20]])
+print(test)
+test = resizeLayer(test)
+print()
+print(test)
+
+# filename = 'book_fausett_small.jpg'
+# resizeImage(filename)
diff --git a/numerical/scipy_interp.py b/numerical/scipy_interp.py
new file mode 100644
index 0000000..fb7d3e8
--- /dev/null
+++ b/numerical/scipy_interp.py
@@ -0,0 +1,11 @@
+import numpy as np
+
+from scipy import interpolate
+x = np.asarray(range(2))
+y = np.asarray(range(2))
+z = np.asarray([[10, 40], [30, 20]])
+f = interpolate.interp2d(x, y, z, kind='linear')
+
+for x in range(6):
+    for y in range(6):
+        print(x, y, f(x, y))