How do I make EXTRAPVAL a scalar?

ex[Y,Z]=meshgrid(5:5:35,10:5:90);
cl=reshape(v,17,7);
cd=reshape(w,17,7);
bal=reshape(x,17,7);
Map1=interp2(cl,cd,bal,a,b);
surf(Map1,Y,Z)

v, w, and x all represent xlsreads. a and b are single numbers prompted by the user.

I am trying to graph these points on a 3d surface plot, but I always get the error using interp2: EXTRAPVAL must be a scalar. When I move certain variables around, the error then becomes: not monotonically increasing.

Please help, I can not figure this out.

[Stephen23]

I don't get any error:

>> [Y,Z] = meshgrid(5:5:35,10:5:90);
>> cl = reshape(1:17*7,17,7);
>> cd = reshape(sqrt(1:17*7),17,7);
>> bal = reshape(pow2(1:17*7),17,7);
>> Map1=interp2(cl,cd,bal,1,2)
Map1 =  16
>> Map1=interp2(cl,cd,bal,1:5,2:6)
Map1 =
           16.00000      3948062.11765   1010638366.11765                 NA                 NA

[madhan ravi]

When surf is used the first argument cannot be a scalar.

[Cory Runnells]

prompt='What is the front ride height?: ';
a=input(prompt,'s');
prompt='What is the rear ride height?: ';
b=input(prompt,'s');

This is the beginning of my code for my a and b variables. When I try using numbers in my Map1 definition (such as 1,2 or 1:5,2:6 as you used), I then get the error: Input grid is not a valid MESHGRID. When I change them back to a,b I again recieve the EXTRAPVAL must be a scalar error.

[madhan ravi]

did you see my answer ? @Cory

[Cory Runnells]

@madhan ravi Surf is not where I am currently having the issue. This error occurs during the interp2 line of code and the program will not advance.

[Steven Lord]

The problem with the code you posted two comments above is the 's' in your input statements. When you use 's' in input it returns what the user entered as text, not as numbers. Because of that, I believe MATLAB interprets your interp2 call as the "Vq = interp2(V, Xq, Yq, METHOD, EXTRAPVAL)" signature instead of "Vq = interp2(X, Y, V, Xq, Yq)".

Instead, have input return what the user entered as numbers.

prompt='What is the front ride height?: ';
a=input(prompt);
prompt='What is the rear ride height?: ';
b=input(prompt);

Answer 1

[madhan ravi]

EDITED

[Y,Z]=meshgrid(5:5:35,10:5:90);
cl=reshape(v,17,7);
cd=reshape(w,17,7);
bal=reshape(x,17,7);
prompt='What is the front ride height?: ';
a=input(prompt);
prompt='What is the rear ride height?: ';
b=input(prompt);
ab=[a b];
[A,B]=meshgrid(min(ab):0.25:max(ab)); %reduce the step size if finer grid is wanted
Map1=interp2(cl,cd,bal,A,B);
surf(Map1,Y,Z)

https://in.mathworks.com/help/matlab/ref/interp2.html#btyq8s0-2_1 meshgrid should be used! before interp2

[Cory Runnells]

Thanks so much @madhan ravi!

[madhan ravi]

Anytime :)

[Cory Runnells]

Ok, I assumed your code would work, but I am still recieving the same error: Input grid is not a valid MESHGRID. Any more ideas?

[madhan ravi]

upload your datas as .mat file to test

Answer 2

[Cory Runnells]

There's bunches of garbage code at the bottom since I'm testing things. But see if you can spot the error

[madhan ravi]

attach your excel file and remove the inputs and just fill it up with values , please make it easier for us debug

[Cory Runnells]

Hopefully this makes it easier

[madhan ravi]

provide the input values .... a,b,c,,,etc..

[Cory Runnells]

a=6 b=7 c=8 d=9; really any input values are what I want to work.

[madhan ravi]

ok cory , you can unaccept my answer , Star Strider is really an expert in this , he can easily debug it.

Answer 3

[Stephen23]

Add str2double:

a = str2double(input(prompt,'s'));
...
b = str2double(input(prompt,'s'));

This is more robust than calling input without the 's' option.