I try to replicate the example from
Example: Polynomial Interpolation (ptc.com)
How Ian I plot the red error bars?
Ho can I plot the red error bars from plot with polyint?
The main reason for your attempt failing is that the example is badly setup, to say the least.
The range variable r is used to index matrices/vectors on one hand also as x-values on the other. This only works for special occasions.
Here is what IMHO is a better approach which lets you select the number of intervals independent of what exactly the x-values are:
N:=32 duplicates the results of the help example,
N:=64 should give you what you obviously had in mind
P6 sheet attached
r:=0..max(x)-min(x) works fine (from example from Mathcad help pages)
I don't see the problem?
Works fine, as long as you do NOT type a comma (,) after 0.05
Unfortunately in my case your solution does not work. If you change the statement
r:=0..max(x)-min(x) to r:=0,0.05..max(x)-min(x)
then the next statements do not work anymore (underline r is flagged as error)
The variable r is defined as a range from 0 to the difference between the highest and lowest values in array x.
Without specifying the second value of that range, you get a range containing only integers 0, 1, 2, 3 ...
This is used for indexing into arrays.
If you change that range to include non-integer values, such as 0.05, then it will start with:
0, 0.05, 0.1, 0.15, 0.2 ...
But those values cannot all be used to index into an array, because for indexing into an array, you can ONLY use integers. That's what the error message is about.