# Summing up two graphs with different starting point

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Kushagra Mehrotra on 16 Mar 2021
Commented: Kushagra Mehrotra on 16 Mar 2021
Hey Matlab Community,
I have two graphs as seen from the figure below and I need to sum them up.
For the graph I have 4 separate column vectors. So for Red I have two separate column vectors with X and Y values and similarly for Blue I have two separate X and Y values The challenge is they both start from different point. The Red one starts at 25C and the Blue one starts at 170C. How can I plot the sum of graphs ? ( Just to clarify the resulting graph should be exactly equal to red graph until 170C and then it would start to deviate because of the addition of Blue.)
I hope I managed to explain the challenge I am facing. Any help would be greatly appreciated.
Thanks and Greetings
Kush

ANKUR KUMAR on 16 Mar 2021
Edited: ANKUR KUMAR on 16 Mar 2021
Method 1: Using boolean
clc
clear
YY=rand(151,2);
XX=[[50:5:800]' [175:5:925]']
data=[XX(:,1) YY(:,1) XX(:,2) YY(:,2)]
plot(data(:,1), data(:,2),'k');
hold on
plot(data(:,3), data(:,4),'b');
uniq=unique([data(:,1);data(:,3)]);
for kk=1:length(uniq)
index1=find(data(:,1)==uniq(kk));
if ~isempty(index1)
value1(kk)=data(index1,2);
else
value1(kk)=nan;
end
index2=find(data(:,3)==uniq(kk))
if ~isempty(index2)
value2(kk)=data(index2,4);
else
value2(kk)=nan;
end
end
hold on
plot(uniq,value1+value2,'r')
Method 2: Interpolation
clc
clear
% generating random data
YY=rand(151,2);
XX=[[50:5:800]' [175:5:925]']
data=[XX(:,1) YY(:,1) XX(:,2) YY(:,2)]
plot(data(:,1), data(:,2),'k');
hold on
plot(data(:,3), data(:,4),'b');
uniq=unique([data(:,1);data(:,3)]);
value1=interp1(data(:,1),data(:,2),uniq);
value2=interp1(data(:,3),data(:,4),uniq);
plot(uniq,value1+value2,'r')
##### 1 CommentShowHide None
Kushagra Mehrotra on 16 Mar 2021
Ohh wow, this is incredible !
Thank you so much for taking time out and writing a code to help me, you are a saviour ! I will try to run the code and Accept the answer ASAP. Again thanks for the time you took to formulate that !

R2020b

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