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

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The Merchant
The Merchant 2019-12-4
编辑： Image Analyst 2019-12-15
"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
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Stephen23
Stephen23 2019-12-15
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

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采纳的回答

Stephen23
Stephen23 2019-12-4
编辑：Stephen23 2019-12-4
[~,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.

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