GNU Octave Matlab: Plot tick labeling

Question

I am making a frequency plot and I would like some help on tick labeling. Here is what I have:

semilogx([200,1000,5000], [0,6,0]);
xlim([20 20000]);
sc = [20:10:100,125:25:175];
scale = [sc,sc*10,sc*100, 20000];
xticks(scale);
xticklabels(scale);
set(gca,'XMinorTick','Off')
grid on;
set (gca, "xminorgrid", "off")
xlabel('frequency (Hz)');
ylabel('dB');

1. How can I make all numbers from 1000 and upwards appear as 1K, 2K, 5K and so on?
2. How could I make the lines on 50,100,200,500,1K,2K,5K,10K appear thicker/more black?

Answer 1

In MATLAB

* I unfortunately could not yet find how to bold the specific lines

Adding the following code allows the ticks to converted to the new names/format suggested in part 1. For part 2 the best I could find out right now is bolding the specific numbers, unfortunately not the specific ticks/lines. Here \bf indicates which labels are to be bolded. All the names will correspond to the positions set originally by your axis vector scale . The last line in the code below indicates the replacement of the current axis, gca .

semilogx([200,1000,5000],[0,6,0]);
sc = [20:10:100,125:25:175];
scale = [sc,sc*10,sc*100, 20000];

Current_Axis = gca;
Current_Axis.XMinorTick = 'off';
xlabel('frequency (Hz)'); ylabel('dB');
xlim([20 20000]);
grid on;

X_Scale_Names = {'\bf20'; '30'; '40'; '\bf50'; '60';
'70';'80';'90';'\bf100';'125';'150';'175';'\bf200';'300';'400';
'500';'600';'700';'800';'900';'\bf1K';'1.25K';'1.5K';'1.75K';
'\bf2K';'3K';'4K';'\bf5K';'6K';'7K';'8K';'9K';'\bf10K';'12.5K';'15K';
'17.5K';'20K'};

---

To Adjust More Grid and Axis Properties:

Current_Axis = gca;
set(Current_Axis,'xtick',scale,'xticklabel',X_Scale_Names);
Current_Axis.LineWidth = 1;
Current_Axis.GridColor = 'k';
Current_Axis.GridAlpha = 0.5;

Ran using MATLAB R2019b

Answer 2

Octave approach (probably works on matlab too though)

I wouldn't rely on latex trickery to do this to be honest.
Here is the way I usually do stuff like this.
Effectively, because the axis labels object is considered a single object, and you cannot split it into parts, the trick is to overlay an invisible, bare-minimum axes object defining only the labels you want, and treat those as you'd like (eg adjust its fontweight, fontsize, xcolor, etc etc).

H = semilogx([200,1000,5000], [0,6,0]);
A = gca();
B = axes();

subscale = [20:10:100,125:25:175];
scale    = [subscale,subscale * 10,subscale * 100, 20000];

ScaleTextLabels = {};
for i = 1 : length( scale )
    if scale(i) >= 1000, ScaleTextLabels{i} = sprintf("%dk", scale(i) / 1000 );
    else,                ScaleTextLabels{i} = num2str( scale(i) );
    end
end

SpecialTickLabels   = { '50', '100', '200', '500', '1k', '2k', '5k', '10k'};
ScaleIndices        = 1 : length( ScaleTextLabels );
SpecialIndices      = nthargout( 2, @ismember, SpecialTickLabels, ScaleTextLabels );
NormalIndices       = setdiff( ScaleIndices, SpecialIndices );

set( A, 'xgrid', 'on', 'xlabel', 'frequency (Hz)', 'xlim', [20 20000]      , 'xminorgrid', 'off', 'xminortick', 'off', 'xticklabel', ScaleTextLabels(NormalIndices),  'xtick', scale(NormalIndices) , 'ylabel', 'dB', 'gridlinestyle', ':', 'gridcolor', 'k', 'gridalpha', 0.5 );
set( B, 'xgrid', 'on', 'xlabel', ''              , 'xlim', get( A, 'xlim' ), 'xminorgrid', 'off', 'xminortick', 'off', 'xticklabel', ScaleTextLabels(SpecialIndices), 'xtick', scale(SpecialIndices), 'ylabel', ''  , 'color', 'none', 'fontsize', 12, 'fontweight', 'bold', 'position', get( A, 'position'), 'xcolor', [0,0,0], 'xscale', 'log', 'ylim', get( A, 'ylim'), 'ytick', [], 'gridlinestyle', '--', 'gridcolor', 'k', 'gridalpha', 0.8 );

This "layers of transparent axes objects" technique is very useful to keep in mind in general, it allows great flexibility when designing complex graphs. :)

Answer 3

I did it like this:

semilogx([200,1000,5000], [0,6,0]);
xlim([20 20000]);
sc = [20:5:35,40:10:100,125:25:175];
scale = [sc,sc*10,sc*100, 20000];
xticks(scale);
xticklabels(scale);
set(gca,'XMinorTick','Off')
grid on;
set(gca,'gridlinestyle',':');
set(gca,'gridalpha',0.6);
set (gca, "xminorgrid", "off");
xg = [50,100,200,500,1000,2000,5000,10000]; #highlight grids
xx = reshape([xg;xg;NaN(1,length(xg))],1,length(xg)*3);
yy = repmat([ylim() NaN],1,length(xg));
line(xx,yy,'Color',[0.65,0.65,0.65]);
xlabel('frequency (Hz)');
ylabel('dB');
X_Scale_Names = {'\fontsize{11}\bf20'; '25'; '30';'35';'40'; '\fontsize{11}\bf50'; '60';
'70';'80';'90';'\fontsize{11}\bf100';'125';'150';'175';'\fontsize{11}\bf200';'250';'300';'350';'400';
'\fontsize{11}\bf500';'600';'700';'800';'900';'\fontsize{11}\bf1K';'1.25K';'1.5K';'1.75K';
'\fontsize{11}\bf2K';'2.5K';'3K';'3.5K';'4K';'\fontsize{11}\bf5K';'6K';'7K';'8K';'9K';'\fontsize{11}\bf10K';'12.5K';'15K';
'17.5K';'\fontsize{11}\bf20K'};
set(gca,'xtick',scale,'xticklabel',X_Scale_Names);

But I don't think this is the best/fastest/easiest way to do it...