I have a two part question regarding structs and Geotiffs; How do I assign NaN to values in a struct? And how do I extract the axes automatically from the R file made in Geotiffread?

    %%AHN2

    tiles = {'r02cn1', 'r02gz2', 'r02hz1', 'r07dn1', 'r07dz1'};
    tiles2= {'R_r02cn1_AHN2', 'R_r02gz2_AHN2', 'R_r02hz1_AHN2', 'R_r07dn1_AHN2', 'R_r07dz1_AHN2'};
    for v = 1:length(tiles)
    fileAHN2_05m = ['Geconverteerde data/ahn2/ahn2_05_ruw/' ...
                     char(tiles(v)), '/' char(tiles(v)), '.tif'];
    [AHN2.(tiles{v}), R_AHN2.(tiles2{v})] = geotiffread(fileAHN2_05m);

    AHN2.(tiles(v))(AHN2.(tiles(v)) <-3.4028234e+38) = NaN

    figure;
    h = imagesc([230000 235000],[587500 581250],AHN2);
    caxis([-5 20]);
    set(h,'AlphaData',~isnan(AHN2));
    k = colorbar;
    title('AHN2','interpreter','none')
    axis square
    %set(get(k,'title'),'string','m','fontsize',12,'fontweight','bold');
    set(get(k,'title'),'string','m','fontsize',12);
    set(gca,'YDir','normal');

    end