diff --git a/A6-simscape-nass/nass_2_hac.m b/A6-simscape-nass/nass_2_hac.m
index 81082bd..f4a2c1d 100644
--- a/A6-simscape-nass/nass_2_hac.m
+++ b/A6-simscape-nass/nass_2_hac.m
@@ -591,11 +591,11 @@ tiledlayout(3, 1, 'TileSpacing', 'compact', 'Padding', 'None');
 
 ax1 = nexttile([2,1]);
 hold on;
-plot(f, abs(squeeze(freqresp(Khac(i,i)*G_hac_m1( i,i), f, 'Hz'))), ...
+plot(f, abs(squeeze(freqresp(Khac(1,1)*G_hac_m1( 1,1), f, 'Hz'))), ...
      'color', [colors(1,:), 0.5], 'DisplayName', '1kg');
-plot(f, abs(squeeze(freqresp(Khac(i,i)*G_hac_m25(i,i), f, 'Hz'))), ...
+plot(f, abs(squeeze(freqresp(Khac(1,1)*G_hac_m25(1,1), f, 'Hz'))), ...
      'color', [colors(2,:), 0.5], 'DisplayName', '25kg');
-plot(f, abs(squeeze(freqresp(Khac(i,i)*G_hac_m50(i,i), f, 'Hz'))), ...
+plot(f, abs(squeeze(freqresp(Khac(1,1)*G_hac_m50(1,1), f, 'Hz'))), ...
      'color', [colors(3,:), 0.5], 'DisplayName', '50kg');
 for i = 2:6
     plot(f, abs(squeeze(freqresp(Khac(i,i)*G_hac_m1( i,i), f, 'Hz'))), 'color', [colors(1,:), 0.5], 'HandleVisibility', 'off');