# How to find a specific point on a plot and connect it with other points?

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Vishnuvardhan Naidu Tanga 2021 年 11 月 8 日
コメント済み: Mathieu NOE 2021 年 11 月 9 日
Hello all,
I am trying to plot a specific point on th plot. For example at first set of data the maximum y value (at0) is 12. I need to divide it by 2 which gives me the value 6. The nearest corresponding value is in cell A8 i need to plot this value. And simillarly for the other data. I have tried to plot it. But i am not getting the desired results. I have tried and I am attaching the result what i am currently getting. Please help me. Thanks in advance.
My code:
clc
clearvars
close all
data = table2array(Z) ;
N = size(data,2);
Nsp = N/2;
ttlc = {'x=0m', 'x=0.1m', 'x=0.2m', 'x=0.3m', 'x=0.4m', 'x=0.5m', ...
'x=0.75m', 'x=1.0m', 'x=1.25m', 'x=1.5m', 'x=2.0m', 'x=2.5m', 'x=3.0m', 'x=3.5m'};
xofst = [0 100 200 300 400 500 750 1000 1250 1500 2000 2500 3000 3500];
figure(1)
hold on
for k = 1:Nsp
col = [2 1]+2*(k-1);
famp = 5;
datacol1 = data(:,col(1))*famp+xofst(k);
datacol2 = data(:,col(2));
minx(k) = min(datacol1);
maxx(k) = max(datacol1);
miny(k) = min(datacol2);
maxy(k) = max(datacol2);
%%%%%%%%%%%%%%%%%%%%% special code for inner line %%%%%%%%%%%%%%%%%%%%%
x_init = (maxx(k)+minx(k))/2; % initial guess
% find nearest value
aa = round(length(datacol1)/2);
datacol1_pos = datacol1(aa+1:end);
datacol2_pos = datacol2(aa+1:end);
[~,ind_pos] = min(abs(datacol1_pos-x_init));
y_pos(k) = datacol2_pos(ind_pos); % final value
x_pos(k) = datacol1_pos(ind_pos); % final value
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
hp(k) = plot(datacol1, datacol2, 'LineWidth',2);
plot([1;1]*[minx(k) maxx(k)], ([1;1]*ylim).', ':k', 'LineWidth',1)
Line_Coordinates = [minx(1) maxx(1)]-minx(1)+minx(k);
LineLength = diff(Line_Coordinates);
end
plot(minx,maxy,'dr')
plot(minx,maxy,'r')
plot(x_pos,y_pos,'dr')
plot(x_pos,y_pos,'--r')
hold off
hl = legend([hp], ttlc, 'Location','northeastoutside');

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### 採用された回答

Mathieu NOE 2021 年 11 月 9 日
hello
to make it work , you have to remove the NaN content of your data
clc
clearvars
close all
data = table2array(Z) ;
N = size(data,2);
Nsp = N/2;
ttlc = {'x=0m', 'x=0.1m', 'x=0.2m', 'x=0.3m', 'x=0.4m', 'x=0.5m', ...
'x=0.75m', 'x=1.0m', 'x=1.25m', 'x=1.5m', 'x=2.0m', 'x=2.5m', 'x=3.0m', 'x=3.5m'};
xofst = [0 100 200 300 400 500 750 1000 1250 1500 2000 2500 3000 3500];
figure(1)
hold on
for k = 1:Nsp
col = [2 1]+2*(k-1);
famp = 5;
datacol1 = data(:,col(1))*famp+xofst(k);
datacol2 = data(:,col(2));
% remove NaN from data
ind1 = ~isnan(datacol1);
ind2 = ~isnan(datacol2);
ind = ind1 & ind2;
datacol1 = datacol1(ind);
datacol2 = datacol2(ind);
minx(k) = min(datacol1);
maxx(k) = max(datacol1);
miny(k) = min(datacol2);
maxy(k) = max(datacol2);
%%%%%%%%%%%%%%%%%%%%% special code for inner line %%%%%%%%%%%%%%%%%%%%%
x_init = (maxx(k)+minx(k))/2; % initial guess
% find nearest value
aa = round(length(datacol1)/2);
datacol1_pos = datacol1(aa+1:end);
datacol2_pos = datacol2(aa+1:end);
[~,ind_pos] = min(abs(datacol1_pos-x_init));
y_pos(k) = datacol2_pos(ind_pos); % final value
x_pos(k) = datacol1_pos(ind_pos); % final value
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
hp(k) = plot(datacol1, datacol2, 'LineWidth',2);
plot([1;1]*[minx(k) maxx(k)], ([1;1]*ylim).', ':k', 'LineWidth',1)
Line_Coordinates = [minx(1) maxx(1)]-minx(1)+minx(k);
LineLength = diff(Line_Coordinates);
end
plot(minx,maxy,'dr')
plot(minx,maxy,'r')
plot(x_pos,y_pos,'dr')
plot(x_pos,y_pos,'--r')
hold off
hl = legend([hp], ttlc, 'Location','northeastoutside');
##### 2 件のコメント表示 1 件の古いコメント非表示 1 件の古いコメント
Mathieu NOE 2021 年 11 月 9 日
My pleasure !
have a good day

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