MATLAB: Plot same data set on two different y axis scales

different scale y axisMATLABmatrixplot

NOTE: Question has been updated.
Hello all,
I want to plot a matrix (37 x 10) represented by sum_ET10 with 2 different y axis scales; km^3/year (original unit) on y axis lhs & mm/year (new unit) on y axis rhs. My code is shown below; I have also included an image below. Currently, my graph is still incorrect. What I want to do is to have a single plot as opposed to the two plots that I'm getting
%% Getting a 37 x 10 matrix of sum_ET10 & sum_area 
decade = 10;
sum_area = squeeze(sum(reshape(area,size(area,1),decade,[]),2)/10);
sum_ET10 = squeeze(sum(reshape(ET,size(ET,1),decade,[]),2)/10);
% Plot the results
x_decade = 1:10;
f1 = figure(1);
x1 = axes;
plot(x_decade,sum_ET10(1,:),'-ok');
% Query the YTicks
yt = get(x1,'YTick');
% Create new axis based on  existing axis
x2 = copyobj(x1,f1);
% Set new axis transparent
set(x2,'Color','none')
% Remove XTicks 
set(x2,'Xtick',[])
% Display the YTicks on the right side
set(x2,'YAxisLocation','right')
% Converting values to mm/year             
mm_sum_ET10 = yt/2199000*1000000;
% Update labels
set(x2,'YTickLabel',mm_sum_ET10)
grid on;
xlabel(x1,'Decade');
ylabel(x1,'km^3/year');
ylabel(x1,'mm/year');
untitled.jpg
Any help is appreciated. This is my first time doing different scaled axes, so I'm in need of help.
Thank you.

Best Answer

You should be using yyaxis instead of overlaying a 2nd axes which can lead to all sorts of problems.
https://www.mathworks.com/help/matlab/ref/yyaxis.html
Demo:
figure()
yyaxis left
plot(rand(1,20)*1000);
yyaxis right
set(gca, 'ytick', 0:10:100, 'ylim', [0,100], 'Ycolor', 'k')
See the link I provided for examples of yyaxis plots.
update
Applying that to your code would look something like this. The important part is to make sure the y limits of both y axes are set so that ylim(axis1) and ylim(axis2) are merely a conversion of each other. See the two lines below with the tag #important where you should make sure you're scaling the axes correctly. 
% Plot the results
figure();
yyaxis left
plot(x_decade,sum_ET10(1,:),'-ok');
set(gca, 'YLim', [min(sum_ET10(1,:)), max(sum_ET10(1,:))])  % #important

yyaxis right
% Converting values to mm/year             
mm_sum_ET10 = yt/2199000*1000000; % I assume yt is a vector
set(gca,'YTick',mm_sum_ET10, 'YLim', [min(mm_sum_ET10), max(mm_sum_ET10)]) % #important
ylabel('mm/year');
% go back to left axes (main axes)
yyaxis left
grid on;
xlabel('Decade');
ylabel('km^3/year');
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