Legend & Labeling points in a plot
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I'd like to have a legend that shows all tangent lines and curves of my graph, also label points if possible either in the legend or right next to the points themselves. My code doesn't do either currently:
syms a x
y=1/(x-1); m=-1; dy=diff(y);
x1_=subs(dy,a); eq=x1_==m; x1=solve(eq); y1=subs(y,x1);
line=m*(x-x1)+y1;
disp('The tangent line(s) are:')
for k=1:length(x1)
fprintf('y = %s\n',char(line(k)))
f=plot(x1,y1,'.', 'color', 'black','markersize',15); hold on
g=fplot(line); set(g,'color','black','LineStyle', '--'); hold on;
end
h=fplot(y); set(h,'color','blue','Linewidth', 1);
j=xline(0); set(j,'color','black','Linewidth', 1.5)
k=yline(0); set(k,'color','black','Linewidth', 1.5)
xlabel('x'); ylabel('y'); title('Curve & tangent line & points')
legend([g h],{'Tangent line', 'Curve'})
Thanks.
采纳的回答
syms a x
y=1/(x-1); m=-1; dy=diff(y);
x1_=subs(dy,a); eq=x1_==m; x1=solve(eq); y1=subs(y,x1);
line=m*(x-x1)+y1;
disp('The tangent line(s) are:')
for k=1:length(x1)
fprintf('y = %s\n',char(line(k)))
f(k)=plot(x1(k),y1(k),'.', 'MarkerSize',15); hold on
g(k)=fplot(line(k),'--');
end
h=fplot(y,'color','blue','Linewidth', 1);
xline(0,'color','black','Linewidth', 1.5);
yline(0,'color','black','Linewidth', 1.5);
xlabel('x'); ylabel('y'); title('Curve & tangent line & points')
legend([g(:); f(:); h],{'Tangent line 1','Tangent line 2' ,'Point 1','Point 2', 'Curve'})
col={'red','green'};
[f.Color]=deal(col{:});
[g.Color]=deal(col{:});
hold off
6 个评论
Matt J
2025-5-28
You can make them different colors if you want. See revised version.
syms a x
y=1/(x-1); m=-1; dy=diff(y);
x1_=subs(dy,a); eq=x1_==m; x1=solve(eq); y1=subs(y,x1);
line=m*(x-x1)+y1;
disp('The tangent line(s) are:')
disp(char(compose('y = %s',string(line))))
scatlabel( scatter(x1,y1,'k.', 'SizeData',150) ); hold on
g=fplot(line,'k--');
h=fplot(y,'color','blue','Linewidth', 1); hold off
xline(0,'color','black','Linewidth', 1.5);
yline(0,'color','black','Linewidth', 1.5);
xlabel('x'); ylabel('y'); title('Curve & tangent line & points')
legend([g(1); h],{'Tangent line', 'Curve'})
function varargout=scatlabel(H,labels)
%Add labels to the (XData,YData,ZData) coordinates in a plot pointed to by a
%graphics handle object H.
%
% Hout=scatlabel(H) %Labels will be simple enumeration
% Hout=scatlabel(H,labels) %Provided labels can be string or numeric
%
%Hout is a handle to a GraphPlot object containing the labels.
ax=H(1).Parent;
S.XData=[H.XData];
S.YData=[H.YData];
for i=numel(H):-1:1
if isprop(H(i),'ZData') && ~isempty(H(i).ZData),
ZData{i}=[H(i).ZData];
else
ZData{i}=zeros(1,numel(H(i).XData));
end
end
S.ZData=cell2mat(ZData);
N=numel(S.XData);
if nargin<2, labels=1:N; end
assert(numel(labels)==N,'Number of labels doesn''t match number of data points');
tf=ishold;
if ~tf
hold(ax,'on')
end
args={'Marker','none','NodeLabel',labels,'NodeFontSize',12,'HitTest','off',...
'XData', S.XData, 'YData', S.YData};
if isfield(S,'ZData'),
args=[args,{'ZData',S.ZData}];
end
H=plot(ax,graph( speye(N),'omit' ),args{:});
if ~tf
hold(ax,'off')
end
if nargout, varargout={H}; end
end
rezheen
2025-5-28
Matt J
2025-5-28
Yes, you can provide whatever labels you want. From the help doc,
% Hout=scatlabel(H,labels) %Provided labels can be string or numeric
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