# MultivariateNormal with trackedArray Mean and standard Deviation and clamping tracked array

**URL:** <https://discourse.julialang.org/t/multivariatenormal-with-trackedarray-mean-and-standard-deviation-and-clamping-tracked-array/26259>\
**Category:** General Usage\
**Tags:** question, package, statistics\
**Created:** [July 11, 2019, 6:04pm UTC](https://discourse.julialang.org/t/multivariatenormal-with-trackedarray-mean-and-standard-deviation-and-clamping-tracked-array/26259 "2019-07-11T18:04:01Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Elita\_Lobo](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/elita_lobo/32/9267_2.png) [@Elita\_Lobo](https://discourse.julialang.org/u/Elita_Lobo)\
**Post date:** [July 11, 2019, 6:04pm UTC](https://discourse.julialang.org/t/multivariatenormal-with-trackedarray-mean-and-standard-deviation-and-clamping-tracked-array/26259/1 "2019-07-11T18:04:01Z")

</div>

I am trying to create multivariate distributions from mean and standard deviation obtained from neural network. But I am getting the following error:  
MethodError: no method matching MvNormal(::TrackedArray{…,Array{Float32,1}}, ::TrackedArray{…,Array{Float32,1}})  
Closest candidates are:  
MvNormal(::AbstractArray{T\<:Real,1}, !Matched::PDMats.AbstractPDMat{T\<:Real}) where T\<:Real at /Users/elitalobo/.julia/packages/Distributions/Iltex/src/multivariate/mvnormal.jl:190  
MvNormal(::AbstractArray{T,1} where T, !Matched::PDMats.AbstractPDMat) at /Users/elitalobo/.julia/packages/Distributions/Iltex/src/multivariate/mvnormal.jl:195  
MvNormal(::AbstractArray{#s164,1} where #s164\<:Real, !Matched::Array{#s163,2} where #s163\<:Real) at /Users/elitalobo/.julia/packages/Distributions/Iltex/src/multivariate/mvnormal.jl:203

Also, I am unable to clamp trackedArray values. Both of these functions work well when I apply Tracker.data to the matrix . However I need to backpropagate the error through this distribution/matrix so I do not want to untrack the variables. Can someone please tell me how to resolve this issue.  
I am using Flux for back propagating the error.  
Thanks.  
…

```julia
PolicyNetwork(num_inputs, num_actions, hidden_size, init_w,log_std_min::Float32,log_std_max::Float32) =(
        # Taken from https://github.com/jacobcvt12/reparam
        linear1 = Dense(num_inputs,hidden_size,relu);
        linear2 = Dense(hidden_size,hidden_size,relu);
        
        mean_linear = Dense(hidden_size,num_actions);
        log_std_linear = Dense(hidden_size,num_actions);
        model = Chain(linear1,linear2);
        
        function forward(x) 
            #println(model(transpose(x)));
            mean = mean_linear(model(transpose(x)));
            log_std = log_std_linear(model(transpose(x)));
            
            
            #print(size(log_std));
            #todo clamp!(log_std,log_std_min, log_std_max);
            return transpose(mean), transpose(log_std);
        
                end;
        function evaluate(x) 
            epsilon=1e-6;
            #println("size of x");
            #println(size(x));
            mean, log_std = forward(x);
          
            
            std = exp.(log_std);
            z = rand(Normal(0,1));
            temp = mean + std.*z;
            println("Mean");
            get_info(mean);
            
            mean_temp = slicematrix(mean);
            std_temp = slicematrix(std);
            println("mean temp");
            get_info(mean_temp);
            normal_temp = MvNormal.(Tracker.data.(mean_temp),Tracker.data.(std_temp));
            normal_temp = MvNormal.(mean_temp,std_temp);
          
           
          
            
            temp = slicematrix(temp);
           
           
            
            
            
            action = tanh.(mean .+ std.*z);
          
            log_prob = loglikelihood.(normal_temp, temp) ;
            
            
            
            deriv = log.(1.0 .-action.^2 .+ epsilon);
            
           
            log_prob = reshape(log_prob,(1,length(log_prob))) - deriv;
            
            print("done");
            log_prob_sum = sum(log_prob,dims=2);
           
            return transpose(action), transpose(log_prob), z , transpose(mean), transpose(log_std);
            
    
                end;
        function get_action(x) 
        epsilon=1e-6;
            mean = mean_linear(model(x));
            log_std = log_std_linear(model(x));
          
            
            std = exp.(log_std);
            z = rand(Normal(0,1));
            temp = mean + std.*z;
            mean_temp = reshape(mean,(size(mean)[2]));
            std_temp = reshape(std,(size(std)[2]));
           
            normal_temp = Normal.(mean_temp,std_temp);
          
            temp = reshape(temp,(size(temp)[2],1));
          
            
            temp = slicematrix(temp);
              
            action = tanh.(mean .+ std.*z);
          
        return Tracker.data(transpose(action)[1,:]);
                end;
        new(log_std_min,log_std_max,linear1,linear2,mean_linear,log_std_linear,forward,evaluate,get_action)
        ) 
     end
    PolicyNetwork(num_inputs, num_actions, hidden_size) = PolicyNetwork(num_inputs, num_actions, hidden_size,1e-3,Float32(-20.0),Float32(2.0));
function slicematrix(A::AbstractMatrix)
    return [A[i, :] for i in 1:size(A,1)]
end

```

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<div class="post-metadata">

**Author:** ![Elita\_Lobo](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/elita_lobo/32/9267_2.png) [@Elita\_Lobo](https://discourse.julialang.org/u/Elita_Lobo)\
**Post date:** [July 11, 2019, 8:36pm UTC](https://discourse.julialang.org/t/multivariatenormal-with-trackedarray-mean-and-standard-deviation-and-clamping-tracked-array/26259/2 "2019-07-11T20:36:52Z")

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Solved the first issue using Tracker.collect.  
Still not able to clamp tracked array elements.

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<div class="post-metadata">

**Author:** ![improbable22](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/improbable22/32/5464_2.png) [@improbable22](https://discourse.julialang.org/u/improbable22)\
**Post date:** [July 12, 2019, 6:46am UTC](https://discourse.julialang.org/t/multivariatenormal-with-trackedarray-mean-and-standard-deviation-and-clamping-tracked-array/26259/3 "2019-07-12T06:46:05Z")

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You can’t mutate trackedarrays. But you can write `clamp.(param(randn(10)), -1,1)`. Or if you must you can write `clamp!(param(randn(10)).data, -1,1)`.