Why are minor ticks not being added to my graph?

I used this resource to find how to add minor ticks: https://www.mathworks.com/help/matlab/ref/matlab.graphics.axis.decorator.numericruler-properties.html

I added it to my code below but it does not show up on my graph as seen in the picture (found under comments):

figure (1)
scatter(G.Date, G.("Avg_ESDiamiter"), 'LineWidth',1 ) ; 
ax1 = gca ; 
ax1.LineWidth = 1.5 ; 
ax1.XAxis.MinorTick = 'on' ; % Here is where I added minor ticks 
fontsize(gca, 12,'points') ;
xtickformat("MM-dd") ; 
xtickangle(315) ; 

[Kristine]

My photo didn't seem to upload above, so there it is:

Answer 1

[Voss]

To get minor ticks on a datetime axis: In addition to setting the axis ruler's MinorTick property 'on', apparently you have to specify the minor tick values themselves by setting the axis ruler's MinorTickValues property.

(Reference: https://www.mathworks.com/matlabcentral/answers/1579399-is-it-possible-to-get-minor-grid-lines-to-show-when-using-datetime-along-x-axis#answer_824089)

Example:

G = table(datetime(2024,3,(10:16).',0,0,0),randi(10,7,1),'VariableNames',{'Date','Avg_ESDiamiter'})

G = 7x2 table
       Date        Avg_ESDiamiter
    ___________    ______________

    10-Mar-2024          9       
    11-Mar-2024          9       
    12-Mar-2024          1       
    13-Mar-2024          7       
    14-Mar-2024          6       
    15-Mar-2024          1       
    16-Mar-2024          7       

% example minor tick values (interpolate a new value 
% between each consecutive pair of G.Date values):
NG = height(G);
mtv = interp1(1:NG,G.Date,linspace(1,NG,2*NG-1));

mtv(:)

ans = 13x1 datetime array
   10-Mar-2024 00:00:00
   10-Mar-2024 12:00:00
   11-Mar-2024 00:00:00
   11-Mar-2024 12:00:00
   12-Mar-2024 00:00:00
   12-Mar-2024 12:00:00
   13-Mar-2024 00:00:00
   13-Mar-2024 12:00:00
   14-Mar-2024 00:00:00
   14-Mar-2024 12:00:00
   15-Mar-2024 00:00:00
   15-Mar-2024 12:00:00
   16-Mar-2024 00:00:00

if true
    
    figure (1)
    scatter(G.Date, G.("Avg_ESDiamiter"), 'LineWidth',1 ) ; 
    ax1 = gca ; 
    ax1.LineWidth = 1.5 ; 
    ax1.XAxis.MinorTick = 'on' ;  % Here is where I added minor ticks 
    ax1.XAxis.MinorTickValues = mtv; % set the minor tick values
    fontsize(gca, 12,'points') ;
    xtickformat("MM-dd") ; 
    xtickangle(315) ; 
    
end

[Kristine]

Thanks, your suggestions works great. But I don't understand some of the syntax. In the following lines of code:

mtv = interp1(1:NG,G.Date,linspace(1,NG,2*NG-1)).'

what does the period and apostraphy ( .' ) mean/do at the end of that line?

[Walter Roberson]

The .' is (regular) transpose (as opposed to conjugate transpose, which is the ' operator by itself with no period)

linspace() creates a row vector, so interp1() would respond with a row vector. The .' afterwards would change the row vector into a column vector.

It looks to me as if likely the assignment to ax1.XAxis.MinorTickValues would automatically repair row versus column vector, so I am not presently convinced that the transpose is necessary.

[dpb]

See transpose, .' Set a break point at the line and look at the result with/without the transpose.

Nota Bene: the difference between it and ctranspose, ':

[Voss]

Walter is right, the transpose is not necessary; I included it to make mtv show more nicely on the command line. I've edited the answer.

[Kristine]

Thank you!!

[Voss]

You're welcome!

Answer 2

[dpb]

d=datetime(2024,6,3+[0:35],'format','MM-dd'); % datetimes by day
scatter(d,rand(size(d)))
hAx=gca;

hAx.XAxis.MinorTickValues=d;                % daily minor ticks
hAx.XAxis.MinorTick='on';                   % and display...
box on
% this is an as far as I can tell, undocumented trick to turn off the secondary "year" label
hAx.XAxis.TickLabels=hAx.XAxis.TickLabels;  

●

Have to both turn them on and give values...

[Kristine]

Hi, are you saying

hAx.XAxis.TickLabels=hAx.XAxis.TickLabels;

is code that removes the "2024" lable under the x-axis labels?