I keep getting this error--- syntax: invalid iteration specification

New to Julia
1

I am trying to run this code in code in Julia but I keep getting this error which am struggling to correct. syntax: invalid iteration specification

Any help will be much appreciated please. Below is my code:

x = [0, 5, -5, 4, -5] # x cordinates of the circle
y = [0, 0.6, 0.5, -5, -4.5] # y cordinates of the circle
 
coverage=[[1, 0, 0, 0, 1],[0, 0, 0, 1, 1],[1, 0, 0, 0, 1],[0, 0, 1, 1, 1],[0, 0, 0, 1, 1], [0, 1, 0, 0, 1],[0, 0, 1, 1, 0],[0, 0, 0, 1, 0],[1, 0, 0, 0, 0],[1, 1, 0, 0, 0],[0, 1, 0, 0, 0],[0, 0, 1, 0, 0],[0, 0, 1, 0, 0],[1, 0, 0, 0, 0],[0, 0, 0, 1, 0]]
#A=[[2, 3, 4], [3, 2, 5]]
a=[-1, -1, 1.2, 1.2, 1.2, 0.8, 2.5, 2.5, -3, -3, -1.5, 3, 0.9, -3.7, 3.7] #x cordinate of the points
b=[0.2, 0.8, -0.85, 1.2, 0.5, -1.5, -1.3, 1.4, 1.5, -1.3, -0.8, -2.7, -2.4, 0.5, 0.8] #y cordinate of the points
r=[]        # array to store max distances for the center of each circle to each point
#print("A =", A)
print("A =", coverage)

function  distance()
    for i,xv in enumerate(x):
        R=[] # store the distance of each circle i to each point
        for j, jv in enumerate(a):
            if (coverage[j][i]==1):
               R.append( ((x[i]-a[j])**2 + (y[i]-b[j])**2)**0.5)
        r.append(max(R)) # find maximum distance from circle i to each point and save in r 
           # end
    return r
    
distance()
2

Hi, this looks like a badly formatted incomplete translation from Python to Julia. Would you be so kind as to use triple back ticks to mark down your code?

With regard your question: putting your tuples into brackets like

    for (i, xv) in enumerate(x)

should help.

4 Likes
3

it’s not valid Julia code
it should be something like this


function distance(x, y, a, b) 
    r = Float64[]
    for (i,xv) in enumerate(x)
        R = Float64[]
        for (j, jv) in enumerate(a)
            if coverage[j][i] == 1
                push!(R, ((x[i]-a[j])^2 + (y[i]-b[j])^2)^0.5)
            end
            if length(R) > 0
                push!(r, maximum(R))
            end
         end
    end
    return r
end

Although that is still not optimal because of the allocation of R and pushing to r inside the loop.

I believe you should calculate the values for R and extract the r separately.

1 Like
4

Thank you very much. I tried that but had this displaying now instead of the output I desire. It reads:

distance (generic function with 2 methods)

Can you please help me correct this in other to display the values of r?

thank you

5

you have to call the function

distance(x, y, a, b)

which will display the returned r

1 Like
6

Thank you

1 Like
7

I accidentally missed out passing coverage as an argument

But I hope you can get to grips with it all

8

I was trying to figure that out.
Where should I put that in my code?

9

I am very new to Julia. The syntax of python sometimes confuses me with Julia. I hope to improve gradually in the near future. Thank you very much for your help.

2 Likes
10

just as another argument

function distance(x, y, a, b, coverage)
1 Like
11

Thank you very much. This works perfectly now but giving me all the distances calculated for R. I want to take the maximum value of each of this distances stored in “R” and save it “r”. I am expecting only 5 outputs in all. Is there any way I can achieve this?

12

Seems we ran into the problem of using significant whitespace so appending to r ended up inside the inner loop.

Here I have moved it outside.

function distance(x, y, a, b, coverage) 
    r = Float64[]
    for (i,xv) in enumerate(x)
        R = Float64[]
        for (j, jv) in enumerate(a)
            if coverage[j][i] == 1
                push!(R, ((x[i]-a[j])^2 + (y[i]-b[j])^2)^0.5)
            end
         end
         if length(R) > 0
             push!(r, maximum(R))
         end
    end
    return r
end
13

You mean as a visual indicator, right? The fault was a misplaced end, the indentation is luckily irrelevant here :smiley:

14

This works perfectly now. Thank you very much for the help.
Highly appreciated

1 Like