error bars on plot
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Joseph
am 2 Nov. 2015
Kommentiert: Star Strider
am 2 Nov. 2015
Hello. I am having trouble adding error bars to this plot. My code is below. I need the data "cd_water, re_water..cd_glycol, re_glycol...etc.." all to show error bars from the original loglog plot of CD vs Re. please help. thank you.
Re = logspace(-2,7,1001);
term1 = (24./Re);
term2 = ((2.6*(Re./5))./(1+((Re./5).^1.52)));
term3 = ((0.411*((Re./263000).^(-7.94)))./(1+((Re./263000).^(-8))));
term4 = ((Re.^(0.8))./461000);
CD = term1 + term2 + term3 + term4;
figure(2)
loglog(Re,CD)
grid on
xlabel('Re');ylabel('C_D');
hold on
Cd_water = [0.381, .324, 0.297, 0.214, 0.321];
Re_water = [70221.78, 41366.93,166202.97, 101691.09, 34306.93];
Cd_glycol = [.602,.757,.324,.402,.975];
Re_glycol = [3672.43,1720.25,10375.76,4843.64,1230.25];
Cd_glycerin = [45.4,130,11.4,33.1];
Re_glycerin = [12.89,4.13,57.19,17.47];
plot(Re_water,Cd_water,'*',Re_glycol,Cd_glycol,'.',Re_glycerin,Cd_glycerin,'o')
legend('Expected','Water','Glycol','Glycerin')
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Akzeptierte Antwort
Star Strider
am 2 Nov. 2015
I do not see that you called the errorbar function. If you did, and you did not include it in the code you posted, how did you specify or calculate the error bars, and how did you call the errorbar function with your plots? (If you want to plot more than one plot in an axes object, for example one plot with error bars and one plot without them, you have to use the hold function.)
2 Kommentare
Star Strider
am 2 Nov. 2015
If you just want lines from the curve to the plotted points, errorbar is probably not what you want. You need to program the lines specifically. Fortunately, that isn’t difficult, but does look a bit strange. I had to make some minor changes in your code (creating anonymous functions to allow calculation of the ‘Cd’ values at the specific values of ‘Re’ of your data) to plot the vertical lines.
See if this does what you want:
Re = logspace(-2,7,1001);
term1 = @(Re) (24./Re);
term2 = @(Re) ((2.6*(Re./5))./(1+((Re./5).^1.52)));
term3 = @(Re) ((0.411*((Re./263000).^(-7.94)))./(1+((Re./263000).^(-8))));
term4 = @(Re) ((Re.^(0.8))./461000);
CD = @(Re) term1(Re) + term2(Re) + term3(Re) + term4(Re);
figure(2)
loglog(Re,CD(Re))
grid on
xlabel('Re');ylabel('C_D');
hold on
Cd_water = [0.381, .324, 0.297, 0.214, 0.321];
Re_water = [70221.78, 41366.93,166202.97, 101691.09, 34306.93];
Cd_glycol = [.602,.757,.324,.402,.975];
Re_glycol = [3672.43,1720.25,10375.76,4843.64,1230.25];
Cd_glycerin = [45.4,130,11.4,33.1];
Re_glycerin = [12.89,4.13,57.19,17.47];
plot(Re_water,Cd_water,'*',Re_glycol,Cd_glycol,'.',Re_glycerin,Cd_glycerin,'o')
hold on
plot([Re_water; Re_water], [CD(Re_water); Cd_water], '-r')
plot([Re_glycol; Re_glycol], [CD(Re_glycol); Cd_glycol], '-r')
plot([Re_glycerin; Re_glycerin], [CD(Re_glycerin); Cd_glycerin], '-r')
hold off
legend('Expected','Water','Glycol','Glycerin')
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