How to plot min and max values on graph

I've created some formulas and a function that is composed of if and elseif statements and plots a graph of it. However I am needing for the graph to show the max and min of the curve and I am unsure of how to do so.

X = 0:0.1:10;
Y = (X.^(1.01))+4*cos((3/4).*X.*pi) - 2*sin((2/3)*pi.*X)-0.25;
figure(); %creates figure window
plot (Y,'-r+') %plots figure
xlabel('Time (mins)') %x axis label
ylabel('Density Altitude (km)') %y axis label

function minmax_i = min_max(Y) %function code
N = ones(1,7); 
for i = 2:(length(Y)-1) 
    
    if (Y(i-1) > Y(i)) && (Y(i+1) > Y(i)) %if true, local minimum
        minmax_i(N) = i;
        N = N+1;
    elseif (Y(i-1) < Y(i)) && (Y(i+1) < Y(i)) %if true, local maximum
        minmax_i(N) = i;
        N = N+1;
    end 
end 

end

Answer 1

[KSSV]

X = 0:0.1:10;
Y = (X.^(1.01))+4*cos((3/4).*X.*pi) - 2*sin((2/3)*pi.*X)-0.25; 

% min
[val0,idx0] = min(Y) ;
% max
[val1,idx1] = max(Y) ; 

plot(X,Y)
hold on
plot(X(idx0),Y(idx0),'*r')
plot(X(idx1),Y(idx1),'*b')

Answer 2

[Alan Stevens]

If you meant you want to highight all the peaks and troughs then the following will do it (assuming you haven't got the findpeaks function available):

X = 0:0.01:10;
Y = (X.^(1.01))+4*cos((3/4).*X.*pi) - 2*sin((2/3)*pi.*X)-0.25;

% Peaks and troughs
% Gradient of curve
dYdX = 1.01*X.^0.01 - 3*pi*sin((3/4).*X.*pi) - (4/3)*pi*cos((2/3)*pi.*X);
signchange = diff(sign(dYdX));  % Where curve turns over
idxpos = signchange<0;          % Peak positions
idxneg = signchange>0;          % Trough positions

figure(); %creates figure window
plot(X,Y,'r',X(idxpos),Y(idxpos),'bo',X(idxneg),Y(idxneg),'bs'),grid
xlabel('Time (mins)') %x axis label
ylabel('Density Altitude (km)') %y axis label

[Steven Lord]

You could use the islocalmin and islocalmax functions included in MATLAB.