Calculate Standard Deviation on a Certain X Point

Hi!

So now I have obtained a linear fit according to scatter plots of 10 data sets with different sizes. The data sets consists of millions of displacement data on fixed force value, in the multiples of 9.81. Now I want to calculate the standard deviation of displacement value on each force value, namely 9.81,19.62 etc...Is there any way to do it fast in Matlab?

I have attached my code here too.

[Jan]

How can the force values be classified to groups?

[Huichen Zhang]

Yes it will be much better if the force values can be classified to groups. I want to group the displacement value with force input of 9.81 together, displacement value with force input of 19.62 together etc. However, now a dataset now consists of displacement with force inputs of 9.81,19.62...., and a total dataset, which is simply merging all data sets together, consists of displacement with force inputs of 9.81,19.62...;then again 9.81,19.82...;then again 9.81,19.62...; is there any fast way to group?