If else for class of data

Hi all,

I have been trying to create a function which plots two inputs against each other and their derivatives against eachother on the same plot. I indend to use this function with data from a timetable. I want to be able to use a datetime input or a double in my xdata, so when xdata is a double it simply plots dx against dy, or when xdata is a datetime variable xdata is plotted against dy. Below is my function;

function createFig2(xdata,ydata) %xdata is either double or datetime, ydata is double
    plot(xdata,ydata,'-k')      %plot inputs
    hold on
        if class(xdata) == char('double')       %check if xdata is double
            dx = diff(xdata);
            dy = diff(ydata);
            plot(dx,dy,'--r')
        else    %if xdata is datetime
            dy = diff(ydata);
            plot(xdata,dy,'--r') %plot xdata against dy
        end
    hold off
    xlabel('xdata')
    ylabel('ydata')
end

When I attempt to run this function I get an error in Line 4;

"Matrix dimensions must agree.

Error in createFig2 (line 4)

if class(xdata) == char('double')".

I am not very familiar with ifelse statements or logically statements in matlab so I'm not sure how to fix this. Thank you in advance for your help! :)

Answer 1

[Walter Roberson]

if isa(xdata, 'double')

Or

if strcmp(class(xdata), 'double')

or

if class(xdata) == "double"       %notice this is not 'double' but "double" 

[Carl Mappas]

Thanks Walter. I used your third suggestion :)

[Cameron]

Another option

if class(xdata) == string('double')

[Walter Roberson]

string('double') is less efficient than "double", but was needed for the very first release that supported string datatype