title: Commit mutation in a different Vuex module
body: <p>I got the following structure:</p>
  <pre><code>store.js
  |
  |-- yields.js
  |
  |--analysis (sub-folder)
            |
            |
            ---actions.js
            |
            ---mutations.js
            |
            ---state.js
  </code></pre>
  <p>In mutations.js I set the date of a state in state.js like:</p>
  <pre class="lang-js prettyprint-override"><code>stateFetchParamsStart: (state, input) =&gt; {
    state.fetchParams.start = input;
    // Want to change yields.PRdate too
    //state.yields.PRdate = input;
  }
  </code></pre>
  <p>How can I access the PRdate state of yields.js with the mutation from state.js?</p>
  <hr />
  <p>EDIT with more information:</p>
  <p>I'm setting initial values of <code>PRdate</code> when the component is mounted like:</p>
  <pre class="lang-js prettyprint-override"><code>mounted(){
    ...
    this.fetchPRData(this.pvSystem.system_id); // makes an axios call
  }
  </code></pre>
  <p>Also I've set a computed property asking for the date:</p>
  <pre class="lang-js prettyprint-override"><code>getPrDate: {
    get(){
      return this.$store.state.yields.PRdate;
    }
  }
  </code></pre>
  <p>Now when clicking on a date picker I want the date to change (also computed propery on a <code>v-model</code>):</p>
  <pre class="lang-js prettyprint-override"><code>start: {
    get() {
      return this.$store.state.analysis.fetchParams.start
    },
    set(value) {
      this.$store.commit('stateFetchParamsStart', value)
    }
  }
  </code></pre>