Error changing Dataset using Part in V10

Questions
1

In the new guide Computation With Structured Datasets we can find this part, on how to change a Dataset

CapturadeTela2014-07-09às22.38.53.png

But if we create a Dataset like:

ds=Dataset[{<|"a"->1,"b"->"x"|>,<|"a"->2,"b"->"y"|>,<|"a"->6,"b"->"z"|>}];

And then make:

ds[[1, 1]] = 2

Or, closer to my real case test:

ds[[All, "a"]] = Accumulate@Normal@ds[[All, "a"]]

We get an error:

"Part specification ds[[1,1]] is longer than depth of object"

"Part specification ds[[All,1]] is longer than depth of object. "

Is this a Bug?

Setting is not working on Dataset as stated by documentation.

Without this operation, it’s very difficult to use Dataset in real world applications.

Related post in StackExchange

2

Yes, that appears not to work. Although accessing parts by using things like ds[[All, “a”]] does work as expected.

3

Documentation glitch. Thank you for pointing it out.

I reported it to documentation staff.

Sorry for the inconvenience.

4

Can parts of Dataset be assigned new values as of version 10.0.2.0? If so, what is the syntax?

5

No upgrade for V10.0.2.0.

6

7 years have passed! I still miss this functionality in Dataset.
https://mathematica.stackexchange.com/q/52414/2266