MATLAB: How to display the Xticks from the command line

Question

INTRO: Hi I plot arbitrary data against date ticks for hours of the day as below:

%Get traffic count data
load count.dat
% Create arrays for an arbitrary date, here April 18, 1995
n = length(count);
year = 1990 * ones(1,n);
month = 4 * ones(1,n);
day = 18 * ones(1,n);
% Create arrays for each of 24 hours;
hour = 1:n;
minutes = zeros(1,n);
% Get the datenums for the data (only hours change)
xdate = datenum(year,month,day,hour,minutes,minutes);
% Plot the traffic data against datenums
plot(xdate,count)
% Update the graph's x-axis with date ticks
datetick('x','HHPM')

GOAL: I want to display the XTicks and modified the following lines:

h=subplot(1,1,1);
plot(xdate,count);
set(h,'XTick',xdate)
datetick(h,'x','HH','keepticks')

QUESTION: Why do I need to use subplot to display the XTick? I have also the version suggested by Walter:

h = plot(xdate,count);
haxis = ancestor(h, 'axes');
set(haxis, 'XTick', xdate);
datetick(haxis, 'x', 'HHPM')

but I still obtain the following error:

Error using set
Conversion to double from cell is not possible.

I wonder if someone could help me to correct these command lines and avoid the use of subplot.

Thank you in advance for your help

Emerson

Answer 1

 x = -pi:.1:pi;
y = sin(x);
plot(x,y)
set(gca,'XTick',-pi:pi/2:pi)
set(gca,'XTickLabel',{'-pi','-pi/2','0','pi/2','pi'})
title('Sine Function');
xlabel('Radians');
ylabel('Function Value');