Question

Hi Im a matlab beginner. Would you plz solve my problem? Thanks!
Matlab)
How to make a code about interpolation?(without using interp1,imresize..etc the internal function)

I=[1 10 25 432 28 294 70 80]
How to make the I2 whose length is 11 with linear interpolation?(Without matlab function such as imresize!!)

Answer 1

Explanation : I have sorted the data points. I am finding out the points which are more required. I am using the line equation y = mx + c to find new point between two points.
I have taken the given points as value on y-axis and for x-axis I have considered their position values (1 to number of elements).
so to find out any new point I have used y = y1 + slope*(x - x1)
where y1 is the first point and x1 is its position, slope is (y2-y1)/(x2 - x1)
x2, x1 are the position of points y2, y1.
Below is the function which I have implemented for linear interpolation:
I have considered that len(required length) will be more than or equal to the size of given data points.

function res = linearinterpolation(input,len)
% input is the provided set of points
% len is the required length
inputsize = numel(input);
res = [];
if inputsize == len
res = input;
return;
end
sorteddata = sort(input);
diff = len - inputsize;
%diff has the number of new points required to make.
newpoints = [];
%newpoints vector will be having the new points.
for i = 1 : diff
y1 = sorteddata(i);
y2 = sorteddata(i+1);
x1 = i;
x2 = i+1;
slope = (y2 - y1)/(x2 - x1);
xnew = (i + i+1)/2;
val = y1 + slope * (xnew - x1);
   %using the line equation y = mx + c, more explanation is above
newpoints = [ newpoints , val];
  
end
res = [input , newpoints];

end