CODEWITHSUNDEEP
juliacomplex-numbers
Bifrost
Bifrost

Reputation: 83

Julia BoundsError with less information - don't know why

I have the following code:

# package for ploting functions
using Plots
# use GR
gr()


# nb points to plot
nbPts = 22

# define polar coordinates of a 30 degree (pi/6) rotation
sine = sin(pi/6)
cosine = cos(pi/6)

# scale factor
scale_factor = 0.9




#---------------------------------------
# 1. PLOT POINTS USING ROTATION MATRIX
#---------------------------------------


# define Rotation matrix ( angle = pi/6, center = (0, 0) )
R = zeros(Float64, 2, 2)
R[1,1] = R[2,2]= cosine
R[1,2] = -sine
R[2,1] = sine

# Scale matrix

        ### ...   <-- EXERCISE 4(c): define a uniform scaling matrix (use scale_factor)


# arrays of points coords
X_mat = zeros(nbPts)
Y_mat= zeros(nbPts)

# first Point (1,0)
X_mat[1] = 1.0
Y_mat[1] = 0.0

for i in 2:nbPts

    prevPoint = [X_mat[i-1], Y_mat[i-1]]
    #apply rotation to previous point to obtain new point
    newPoint = R * prevPoint

        ### ...   <-- EXERCISE 4(c): apply scaling matrix

    X_mat[i] = newPoint[1]
    Y_mat[i] = newPoint[2]

end

# plot points in blue
plt1 = scatter(X_mat, Y_mat, color=:blue, xlim = (-1.1, 1.1),  ylim = (-1.1, 1.1), label=false, title="Rotation using matrices" );





#---------------------------------------
# 2. PLOT POINTS USING COMPLEX NUMBERS
#---------------------------------------

function ComplexProduct(z, w)
    (((z[1]*w[1])+(z[2]*w[2])),((z[1]*w[2])+(z[2]*w[1])))

    ### ...   <-- EXERCISE 4(b): implement complex product z * w

end


# first point: z = 1 + 0 * i
Z = ( 1.0, 0.0 )
# second point: w = cosine( pi/6) + sine( pi/6) * i
W = ( cosine, sine )

    ### ...   <-- EXERCISE 4(c): apply scale_factor to W


# arrays of points coords
X_comp = zeros(nbPts)
Y_comp = zeros(nbPts)

# first Point (1,0)
X_comp[1] = Z[1]
Y_comp[1] = Z[2]

for i in 2:nbPts

    prevPoint = (X_comp[i-1], Y_comp[i-1])

    newPoint = ComplexProduct(prevPoint[1], prevPoint[2])   ###  <-- EXERCISE 4(b): compute newPoint by applying rotation to prevPoint (use complex product)

    X_comp[i] = newPoint[1]
    Y_comp[i] = newPoint[2]

end

# plot points in red
plt2 = scatter(X_comp, Y_comp, color=:red, xlim = (-1.1, 1.1),  ylim = (-1.1, 1.1), label=false, title="Rotation using complex numbers" );





# arrange and display
display( plot( plt1, plt2, layout = (1, 2), size=(600*2, 600) ))

The Error: Error Code

The Thing I want: I have to implement a product of complex numbers and this should be used to calculate the rotation with complex numbers.

Should look like that: rotaion

What do I have to change so that the BoundsError is fixed? Don't know what exactly i do wrong because of the poorly information i get from this error log.

Greetings and thanks for the help.

Upvotes: 1

Views: 47

Answers (2)

Bifrost
Bifrost

Reputation: 83

Fixed the bug by changing the following code:

newPoint = ComplexProduct(prevPoint, W)

in line 92

Upvotes: 0

Przemyslaw Szufel
Przemyslaw Szufel

Reputation: 42194

prevPoint[1] is a scalar while your function ComplexProduct expects something that has 2 elements. Perhaps you wanted to pass prevPoint instead of prevPoint[1]?

BTW you use incorrect naming pattern. CamelNaming is discouraged for Julia. Your variable should be named prev_point and your function should be named complex_product.

Upvotes: 2

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