I really need help with fprintf'ing a string, having it alternate with commas and parentheses.

"I really need help with fprintf'ing a string, having it alternate with commas and parentheses."

How do I write a function to fprintf the following string, so that it also changes when the input is changed!:

"convex points: 6 (1 15), 7 (2 6), 8 (6 1), 10 (16 7), 12 (19 18) and 5 (9 19)."

aka

"convex points: firstConvexPoint (coordsX coordsY), secondConvexPoint (coordsX coordsY)"

the values are already sorted properly in arrays, but I can't figure out how to code the string that it alternates in such a way that I get the string above..

Any help is hugely appreciated.

Code:

clear;
close all;
clc;
xy = [
3 12    % Point 1
10 8    % Point 2
11 14   % Point 3
13 16   % Point 4
9 19    % Point 5
1 15    % Point 6
2 6     % Point 7
6 1     % Point 8
12 5    % Point 9
16 7    % Point 10
14 17   % Point 11
19 18   % Point 12
];
xy = xy';
convexHull = getConvexHull(xy);
coords = xy(:,convexHull)';
coordsX = coords(:,1);
coordsY = coords(:,2);
fprintf
function k = getConvexHull(xy) 
[m,n] = size(xy);
    
    if m~=2
        error('convexhull: xy must have 2 columns');
    end
    
    [xmin,first] = min( xy(1,:) );
    ind = [1:(first-1) (first+1):n];
    angle = atan2( xy(1,ind)-xy(1,first), xy(2,ind)-xy(2,first) );
    [junk,order] = sort(angle);
    ind = [ind(order) first];
    stack = zeros( n, 1, 'uint32' );
    stack(1) = first;
    stacktop = 1;
    i = 1;
    while i<=n
        if stacktop<2
            stacktop = stacktop+1;
            stack(stacktop) = ind(i);
            i = i+1;
        else
        p0 = xy(:,stack(stacktop));
        p1 = xy(:,stack(stacktop-1));
        p2 = xy(:,ind(i));
        if (p1(1)-p0(1))*(p2(2)-p0(2))-(p2(1)-p0(1))*(p1(2)-p0(2)) >= 0
            stacktop = stacktop+1;
            stack(stacktop) = ind(i);
            i = i+1;
        else
        stacktop = stacktop-1;
        end
    end
end
    
k = stack(1:stacktop);
k = flip(k);
k(end) = [];
    
end

[Rik]

This is a public forum. You're getting free help from strangers on the internet. The least you can do is leaving your question as it was, so people with a similar question can benefit from your question and the answer. If you want private help, you should hire a consultant.

[Rena Berman]

(Answers Dev) Restored edit

[Stephen23]

Original question (in case this gets deleted for a third time):

"I really need help with fprintf'ing a string, having it alternate with commas and parentheses."

How do I write a function to fprintf the following string, so that it also changes when the input is changed!:

"convex points: 6 (1 15), 7 (2 6), 8 (6 1), 10 (16 7), 12 (19 18) and 5 (9 19)."

aka

"convex points: firstConvexPoint (coordsX coordsY), secondConvexPoint (coordsX coordsY)"

the values are already sorted properly in arrays, but I can't figure out how to code the string that it alternates in such a way that I get the string above..

Any help is hugely appreciated.

Code:

clear;
close all;
clc;
xy = [
3 12    % Point 1
10 8    % Point 2
11 14   % Point 3
13 16   % Point 4
9 19    % Point 5
1 15    % Point 6
2 6     % Point 7
6 1     % Point 8
12 5    % Point 9
16 7    % Point 10
14 17   % Point 11
19 18   % Point 12
];
xy = xy';
convexHull = getConvexHull(xy);
coords = xy(:,convexHull)';
coordsX = coords(:,1);
coordsY = coords(:,2);
fprintf
function k = getConvexHull(xy) 
[m,n] = size(xy);
    
    if m~=2
        error('convexhull: xy must have 2 columns');
    end
    
    [xmin,first] = min( xy(1,:) );
    ind = [1:(first-1) (first+1):n];
    angle = atan2( xy(1,ind)-xy(1,first), xy(2,ind)-xy(2,first) );
    [junk,order] = sort(angle);
    ind = [ind(order) first];
    stack = zeros( n, 1, 'uint32' );
    stack(1) = first;
    stacktop = 1;
    i = 1;
    while i<=n
        if stacktop<2
            stacktop = stacktop+1;
            stack(stacktop) = ind(i);
            i = i+1;
        else
        p0 = xy(:,stack(stacktop));
        p1 = xy(:,stack(stacktop-1));
        p2 = xy(:,ind(i));
        if (p1(1)-p0(1))*(p2(2)-p0(2))-(p2(1)-p0(1))*(p1(2)-p0(2)) >= 0
            stacktop = stacktop+1;
            stack(stacktop) = ind(i);
            i = i+1;
        else
        stacktop = stacktop-1;
        end
    end
end
    
k = stack(1:stacktop);
k = flip(k);
k(end) = [];
    
end

Answer 1

[Stephen23]

[~,idx] = ismember(coords,xy.','rows'); % Better: obtain these indices from your function!
mat = [idx,coords].'; % should have size 3xN for N points.
fprintf('convex points:'); % prints once.
fprintf(' %d (%d %d),',mat(:,1:end-1)) % prints N-1 times.
fprintf(' and %d (%d %d).\n',mat(:,end)) % prints once.

Which prints:

convex points: 6 (1 15), 7 (2 6), 8 (6 1), 10 (16 7), 12 (19 18), and 5 (9 19).

Tip: avoid confusion be not transposing xy all the time: pick one orientation and stick to it.

[The Merchant]

Thank you so much!

Is there maybe an easy-to-do edit so that it says ...18) and 5 (9... instead of ...18), and 5 (9...?

Anyways, very big thanks!