Clear Filters
Clear Filters

Contour plot with different levels for negative and positive values

24 views (last 30 days)
Hi everyone,
I need to build a contour plot to display both positive and negative values of contours. Specifically, I want the contour lines with positive values to be colored in red, while those with negative values should be in blue. The desired appearance of the contour plot is depicted in the figure.
To create the contour plot, I am using a certain code. However, in its current form, this code does not allow for the correct visualization of contour lines with negative values, resulting in gaps. I am unable to adjust the number of contour lines for positive and negative values. I would appreciate your help.
load('fdata.mat')
z=plane(:,2); % axis Z
y=plane(:,1); % axis Y
fdata=plane(:,3); % function
[X,Y]=meshgrid(min(z):0.01:max(z),min(y):0.01:max(y)); % grid
Z=griddata(z,y,fdata,X,Y);
h_plot = figure('InvertHardcopy','on','Color',[1 1 1],'Colormap',[0 0 1;0.00892857182770967 0.00892857182770967 1;...
0.0178571436554193 0.0178571436554193 1;0.0267857145518064 0.0267857145518064 1;0.0357142873108387 0.0357142873108387 1;...
0.0446428582072258 0.0446428582072258 1;0.0535714291036129 0.0535714291036129 1;0.0625 0.0625 1;0.0714285746216774 0.0714285746216774 1;...
0.0803571417927742 0.0803571417927742 1;0.0892857164144516 0.0892857164144516 1;0.0982142835855484 0.0982142835855484 1;...
0.107142858207226 0.107142858207226 1;0.116071425378323 0.116071425378323 1;0.125 0.125 1;0.133928567171097 0.133928567171097 1;...
0.142857149243355 0.142857149243355 1;0.151785716414452 0.151785716414452 1;0.160714283585548 0.160714283585548 1;0.169642850756645 0.169642850756645 1;...
0.178571432828903 0.178571432828903 1;0.1875 0.1875 1;0.196428567171097 0.196428567171097 1;0.205357149243355 0.205357149243355 1;0.214285716414452 0.214285716414452 1;...
0.223214283585548 0.223214283585548 1;0.232142850756645 0.232142850756645 1;0.241071432828903 0.241071432828903 1;0.25 0.25 1;0.258928567171097 0.258928567171097 1;...
0.267857134342194 0.267857134342194 1;0.27678570151329 0.27678570151329 1;0.28571429848671 0.28571429848671 1;0.294642865657806 0.294642865657806 1;0.303571432828903 0.303571432828903 1;...
0.3125 0.3125 1;0.321428567171097 0.321428567171097 1;0.330357134342194 0.330357134342194 1;0.33928570151329 0.33928570151329 1;0.34821429848671 0.34821429848671 1;0.357142865657806 0.357142865657806 1;...
0.366071432828903 0.366071432828903 1;0.375 0.375 1;0.383928567171097 0.383928567171097 1;0.392857134342194 0.392857134342194 1;0.40178570151329 0.40178570151329 1;0.41071429848671 0.41071429848671 1;...
0.419642865657806 0.419642865657806 1;0.428571432828903 0.428571432828903 1;0.4375 0.4375 1;0.446428567171097 0.446428567171097 1;0.455357134342194 0.455357134342194 1;0.46428570151329 0.46428570151329 1;...
0.47321429848671 0.47321429848671 1;0.482142865657806 0.482142865657806 1;0.491071432828903 0.491071432828903 1;0.5 0.5 1;0.508928596973419 0.508928596973419 1;0.517857134342194 0.517857134342194 1;...
0.526785731315613 0.526785731315613 1;0.535714268684387 0.535714268684387 1;0.544642865657806 0.544642865657806 1;0.553571403026581 0.553571403026581 1;0.5625 0.5625 1;0.571428596973419 0.571428596973419 1;...
0.580357134342194 0.580357134342194 1;0.589285731315613 0.589285731315613 1;0.598214268684387 0.598214268684387 1;0.607142865657806 0.607142865657806 1;0.616071403026581 0.616071403026581 1;0.625 0.625 1;...
0.633928596973419 0.633928596973419 1;0.642857134342194 0.642857134342194 1;0.651785731315613 0.651785731315613 1;0.660714268684387 0.660714268684387 1;0.669642865657806 0.669642865657806 1;...
0.678571403026581 0.678571403026581 1;0.6875 0.6875 1;0.696428596973419 0.696428596973419 1;0.705357134342194 0.705357134342194 1;0.714285731315613 0.714285731315613 1;0.723214268684387 0.723214268684387 1;...
0.732142865657806 0.732142865657806 1;0.741071403026581 0.741071403026581 1;0.75 0.75 1;0.758928596973419 0.758928596973419 1;0.767857134342194 0.767857134342194 1;0.776785731315613 0.776785731315613 1;...
0.785714268684387 0.785714268684387 1;0.794642865657806 0.794642865657806 1;0.803571403026581 0.803571403026581 1;0.8125 0.8125 1;0.821428596973419 0.821428596973419 1;0.830357134342194 0.830357134342194 1;...
0.839285731315613 0.839285731315613 1;0.848214268684387 0.848214268684387 1;0.857142865657806 0.857142865657806 1;0.866071403026581 0.866071403026581 1;0.875 0.875 1;0.883928596973419 0.883928596973419 1;...
0.892857134342194 0.892857134342194 1;0.901785731315613 0.901785731315613 1;0.910714268684387 0.910714268684387 1;0.919642865657806 0.919642865657806 1;0.928571403026581 0.928571403026581 1;0.9375 0.9375 1;...
0.946428596973419 0.946428596973419 1;0.955357134342194 0.955357134342194 1;0.964285731315613 0.964285731315613 1;0.973214268684387 0.973214268684387 1;0.982142865657806 0.982142865657806 1;...
0.991071403026581 0.991071403026581 1;1 1 1;1 1 1;1 1 1;1 1 1;1 1 1;1 1 1;1 1 1;1 1 1;1 1 1;1 1 1;1 1 1;1 1 1;1 1 1;1 1 1;1 1 1;1 1 1;1 1 1;1 1 1;1 1 1;1 1 1;1 1 1;1 1 1;1 1 1;1 1 1;1 1 1;1 1 1;...
1 1 1;1 0.991452991962433 0.991452991962433;1 0.982905983924866 0.982905983924866;1 0.974358975887299 0.974358975887299;1 0.965811967849731 0.965811967849731;1 0.957264959812164 0.957264959812164;...
1 0.948717951774597 0.948717951774597;1 0.94017094373703 0.94017094373703;1 0.931623935699463 0.931623935699463;1 0.923076927661896 0.923076927661896;1 0.914529919624329 0.914529919624329;...
1 0.905982911586761 0.905982911586761;1 0.897435903549194 0.897435903549194;1 0.888888895511627 0.888888895511627;1 0.88034188747406 0.88034188747406;1 0.871794879436493 0.871794879436493;...
1 0.863247871398926 0.863247871398926;1 0.854700863361359 0.854700863361359;1 0.846153855323792 0.846153855323792;1 0.837606847286224 0.837606847286224;1 0.829059839248657 0.829059839248657;...
1 0.82051283121109 0.82051283121109;1 0.811965823173523 0.811965823173523;1 0.803418815135956 0.803418815135956;1 0.794871807098389 0.794871807098389;1 0.786324799060822 0.786324799060822;...
1 0.777777791023254 0.777777791023254;1 0.769230782985687 0.769230782985687;1 0.76068377494812 0.76068377494812;1 0.752136766910553 0.752136766910553;1 0.743589758872986 0.743589758872986;...
1 0.735042750835419 0.735042750835419;1 0.726495742797852 0.726495742797852;1 0.717948734760284 0.717948734760284;1 0.709401726722717 0.709401726722717;1 0.70085471868515 0.70085471868515;1 0.692307710647583 0.692307710647583;1 0.683760702610016 0.683760702610016;1 0.675213694572449 0.675213694572449;1 0.666666686534882 0.666666686534882;1 0.658119678497314 0.658119678497314;1 0.649572670459747 0.649572670459747;1 0.64102566242218 0.64102566242218;1 0.632478654384613 0.632478654384613;1 0.623931646347046 0.623931646347046;1 0.615384638309479 0.615384638309479;1 0.606837630271912 0.606837630271912;1 0.598290622234344 0.598290622234344;1 0.589743614196777 0.589743614196777;1 0.58119660615921 0.58119660615921;1 0.572649598121643 0.572649598121643;1 0.564102590084076 0.564102590084076;1 0.555555582046509 0.555555582046509;1 0.547008574008942 0.547008574008942;1 0.538461565971375 0.538461565971375;1 0.529914557933807 0.529914557933807;1 0.52136754989624 0.52136754989624;1 0.512820541858673 0.512820541858673;1 0.504273533821106 0.504273533821106;1 0.495726495981216 0.495726495981216;1 0.487179487943649 0.487179487943649;1 0.478632479906082 0.478632479906082;1 0.470085471868515 0.470085471868515;1 0.461538463830948 0.461538463830948;1 0.452991455793381 0.452991455793381;1 0.444444447755814 0.444444447755814;1 0.435897439718246 0.435897439718246;1 0.427350431680679 0.427350431680679;1 0.418803423643112 0.418803423643112;1 0.410256415605545 0.410256415605545;1 0.401709407567978 0.401709407567978;1 0.393162399530411 0.393162399530411;1 0.384615391492844 0.384615391492844;1 0.376068383455276 0.376068383455276;1 0.367521375417709 0.367521375417709;1 0.358974367380142 0.358974367380142;1 0.350427359342575 0.350427359342575;1 0.341880351305008 0.341880351305008;1 0.333333343267441 0.333333343267441;1 0.324786335229874 0.324786335229874;1 0.316239327192307 0.316239327192307;1 0.307692319154739 0.307692319154739;1 0.299145311117172 0.299145311117172;1 0.290598303079605 0.290598303079605;1 0.282051295042038 0.282051295042038;1 0.273504287004471 0.273504287004471;1 0.264957278966904 0.264957278966904;1 0.256410270929337 0.256410270929337;1 0.247863247990608 0.247863247990608;1 0.239316239953041 0.239316239953041;1 0.230769231915474 0.230769231915474;1 0.222222223877907 0.222222223877907;1 0.21367521584034 0.21367521584034;1 0.205128207802773 0.205128207802773;1 0.196581199765205 0.196581199765205;1 0.188034191727638 0.188034191727638;1 0.179487183690071 0.179487183690071;1 0.170940175652504 0.170940175652504;1 0.162393167614937 0.162393167614937;1 0.15384615957737 0.15384615957737;1 0.145299151539803 0.145299151539803;1 0.136752143502235 0.136752143502235;1 0.128205135464668 0.128205135464668;1 0.119658119976521 0.119658119976521;1 0.111111111938953 0.111111111938953;1 0.102564103901386 0.102564103901386;1 0.0940170958638191 0.0940170958638191;1 0.085470087826252 0.085470087826252;1 0.0769230797886848 0.0769230797886848;1 0.0683760717511177 0.0683760717511177;1 0.0598290599882603 0.0598290599882603;1 0.0512820519506931 0.0512820519506931;1 0.042735043913126 0.042735043913126;1 0.0341880358755589 0.0341880358755589;1 0.0256410259753466 0.0256410259753466;1 0.0170940179377794 0.0170940179377794;1 0.00854700896888971 0.00854700896888971;1 0 0],...
'Color',[1 1 1],'units','normalized','outerposition',[0 0 1 1]);
axes1 = axes('Parent',h_plot);
hold on
zmin = floor(min(z(:)));
zmax = ceil(max(z(:)));
zinc = (zmax - zmin) / 100
zinc = 0.0800
zlevs = zmin:zinc:zmax
zlevs = 1x101
0 0.0800 0.1600 0.2400 0.3200 0.4000 0.4800 0.5600 0.6400 0.7200 0.8000 0.8800 0.9600 1.0400 1.1200 1.2000 1.2800 1.3600 1.4400 1.5200 1.6000 1.6800 1.7600 1.8400 1.9200 2.0000 2.0800 2.1600 2.2400 2.3200
<mw-icon class=""></mw-icon>
<mw-icon class=""></mw-icon>
[L,cL]=contour(X,Y,Z,zlevs);

Accepted Answer

Cris LaPierre
Cris LaPierre on 20 Apr 2024
I'll share my thoughts.
First, in a contour plot, the rows of your matrix correspond to the Y axis, and the columns correspond to X. Therefore, to duplicate the plot you shared, flip y and z.
load fdata.mat
z=plane(:,2); % axis Z
y=plane(:,1); % axis Y
fdata=plane(:,3); % function
% flip y and z in the next 2 lines of code
[X,Y]=meshgrid(min(y):0.01:max(y),min(z):0.01:max(z)); % grid
Z=griddata(y,z,fdata,X,Y);
Next, it does not make sense to me to set your contour line values using anything but your Z value. That is Z here, not z. Perhaps it makes sense for your data. You'd know better than I. However, the range of Z values is so large that I think you want to use logspace to create them. I arrived at these settings through trial and error.
zlevs = logspace(-3,5,26);
Then just call contour twice, once for positive zlevs with solid green lines for the contours, and once with -zlevs with dashed blue contour lines.
contour(X,Y,Z,zlevs,'g-')
hold on
contour(X,Y,Z,-zlevs,'b--')
hold off
  1 Comment
Quark Q
Quark Q on 20 Apr 2024
Dear Cris,
Your solution is great!
I have been struggling to plot in this contour plot for quite some time, but your guidance has enabled me to overcome this challenge. I am truly grateful for your help.

Sign in to comment.

More Answers (0)

Categories

Find more on Contour Plots in Help Center and File Exchange

Products


Release

R2023b

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!