Why Does MATLAB's interp1 Function Throw an Output Argument Error?

[GreenPrint]

RESOLVED

Homework Statement

Hi,

>>v=[1;2;3;4;5;6];
P=[2494 4157;1247 2078;831 1386;623 1039;499 831;416 693];
[P_300,P_500]=interp1(v,P,5.2,'linear')

Error in ==> interp1 at 79
xOffset = 1;

? Output argument "varargout{2}" (and maybe others) not assigned during call to "C:\Program
Files\MATLAB2\R2011a\toolbox\matlab\polyfun\interp1.m>interp1".

I don't understand why I'm getting this error. I'm trying to assign the two values equal to variables. The code runs fine when I try not to assign the values to variables but I would like to assign the values to variables. I don't see what I'm doing wrong.

>> v=[1;2;3;4;5;6];
P=[2494 4157;1247 2078;831 1386;623 1039;499 831;416 693];
interp1(v,P,5.2,'linear')

ans =

  482.4000  803.4000

Thanks in advance!

Homework Equations

The Attempt at a Solution

 

[FrogPad]

You get multiple outputs in a single vector, not [out0, out1, ...] = interp1(...)

Running the code:

v=[1;2;3;4;5;6];
P=[2494 4157;1247 2078;831 1386;623 1039;499 831;416 693];
Q = interp1(v,P,5.2,'linear')

returns:

>> Q

Q =

  482.4000  803.4000

When you are running:

>> v=[1;2;3;4;5;6];
P=[2494 4157;1247 2078;831 1386;623 1039;499 831;416 693];
interp1(v,P,5.2,'linear')

ans =

  482.4000  803.4000

The output (a vector) is stored in the variable "ans" and it is displayed since you are not using ";" to close the line.

 

[GreenPrint]

That makes sense. I didn't realize functions output results into a single vector. I guess I just sort of assumed the opposite. It's something my book never informed me of. Thanks for letting me know.

 

[FrogPad]

yeah no prob.

You *can* have multiple outputs from a function. However, if you look at the comments for interp1 it only shows one output.

Contrast this to "help meshgrid" which has multiple outputs. As an example, you can call the meshgridfunction like:

[X,Y] = meshgrid(x,y) and it will return two outputs.

Note that these are all optional, and if outputs aren't specified, MATLAB throws the first output into the "ans" variable.

 

[DeeNos]

This error is likely due to the fact that you are trying to assign two output values to only one variable. The interp1 function returns two values, P_300 and P_500, but you are only assigning one variable, P_300, to the output. To fix this issue, you can either assign both output values to two different variables, or use the "nargout" function to determine the number of output arguments and assign them accordingly. For example:

[P_300, P_500] = interp1(v,P,5.2,'linear'); %assigning output values to two variables

OR

out = interp1(v,P,5.2,'linear'); %assigning output values to a single variable
[P_300, P_500] = deal(out{:}); %dealing the output values to two variables using the "deal" function