Add 3 trendlines in a scatterplot figure

I have 3 data sets for y and 1 data set for x and I would like to do a scatterplot with 3 trendlines. I was able to create the scatterplots but I dont know how to add a trendline for each data set to my figure. I have tried the basic fitting tool but when I try to add the trendline to the second set of data, the first trendline disappears and I need all three trendlines in the figure.

Here is my code:

%% Load data
dataset=xlsread('sediment_matlab.xls','Sheet1','A1:F14')
Time=dataset(:,1);
A=dataset(:,2);
B=dataset(:,4);
C=dataset(:,6)

scatter(Time,A),xlabel('Time(hours)'),ylabel('[NO3-]'); hold on; scatter (Time,B); hold on; scatter(Time,C)
ttl = sprintf('[Light NO3-]');
title(ttl,'FontWeight','bold', 'FontSize',12, 'FontName','Times New Roman');

[Image Analyst]

You forgot to attach 'sediment_matlab.xls'. And I see no trends in your data, much less 3 trends. Can you indicate where you see trends? Do you want some kind of curve plotted vs. time, like a quadratic or something for each trend???

[SANDRA COSTA]

I just wanted to add 3 trendlines for each data set just like this graph.

Answer 1

[darova]

Use polyfit

a1 = polyfit(Time,A,1);
A1 = polyval(a1,Time);
plot(Time,A1)

[SANDRA COSTA]

Perfect. Thank you so much.