MATLAB: Change bar graph color by sign

bar graphcolor coding

I have a 502×2 column matrix made up of B = [datenum, data]. There are positive nad negative data values, and I want to make all of the positive values red and all of the negative values blue, similar to the figure midway down this page: https://niwa.co.nz/climate/information-and-resources/southern-annular-mode

My code so far is just:

bar(B(:,1), B(:,2))

Is there a straightforward way to do this?

Thank you!

Best Answer

bar(B(B(:,2)>=0,1), B(B(:,2)>=0,2),'FaceColor','b')

hold on

bar(B(B(:,2)<0,1), B(B(:,2)<0,2),'FaceColor','r')

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MATLAB: How can I solve non polynomial equations.

FIRST: see Getting Started. What you posted is not valid MATLAB code.

There may be many solutions, depending on the initial estimates:

R = 0.082;
a = 4.225;
b = 0.037;
T = 320;
eqn1 = @(v1,v2,P) P+(a./v1^2) - R*T/(v1-b);
eqn2 = @(v1,v2,P) P+(a./v2^2) - R*T/(v2-b);
eqn3 = @(v1,v2,P) P*(v1-v2)-R*T*log(v1-b./v2-b)-a*(1./v1 -1./v2);
[Vv,fval] = fsolve(@(b) [eqn1(b(1),b(2),b(3)); eqn2(b(1),b(2),b(3)); eqn3(b(1),b(2),b(3))], ones(3,1))

producing:

Vv =
   1.071530062473936
   1.071530062474078
  21.684426220811453
fval =
   1.0e-11 *
  -0.252597942562716
  -0.001776356839400
  -0.189449129302390

Experiment to get the result you want.

MATLAB: How to apply colors to bar chart.

See my attached demo.

Best Answer

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MATLAB: How can I solve non polynomial equations.

MATLAB: How to apply colors to bar chart.

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