why am i getting an error for counts in histogram?

I am trying to display the counts in my histogram, but I keep getting an error message stating 'Too many output arguments'.

    Speed = HPperformance(:,23);
[n,x] = histogram(Speed.GPSSpeed_knots_);
h.BinEdges = [1:20];
barstrings = num2str(n');
text(x,n,barstrings,'horizontalalignment','center','verticalalignment','bottom')

Answer 1

[Image Analyst]

What kind of variables are HPperformance and Speed? Apparently Speed is a structure. Is HPperformance a structure array? If so, Speed would be a column vector of structures. Since I don't really know what these variables are (yet), about all I can suggest is to try to concatenate the values:

histogram([Speed.GPSSpeed_knots_]);

[Rashdeep Singh]

HPperformance is my main database from which i'm extracting only the GPSspeed and putting it in Speed. the photo of the histogram is attached. I want to show the counts for each bar.

[Image Analyst]

You didn't answer my question. I don't think they are databases. If you do this:

whos HPperformance 
whos Speed

What do you see in the command window when these execute? I don't think it will say that they're "databases" it will say a regular MATLAB variable type like structure, cell array, double, or whatever. Please do that, then read this link first and then paste ALL THE RED TEXT of your error message.