Block diagram TikZ connectors

Question

I am having some issues with the following code:

\documentclass[tikz,border=5mm]{standalone}
    \usetikzlibrary{arrows,positioning,shapes}
\begin{document}

\begin{tikzpicture}[node distance=5mm, >=latex',
 block/.style = {draw, rectangle, minimum height=10mm, minimum width=28mm,align=center},
tblock/.style = {draw, trapezium, minimum height=10mm, 
                 trapezium left angle=75, trapezium right angle=105, align=center},
                        ]
 \node [block]                      (first)     {Bank of England\\ asset purchases};
 \node [block, right=of first]      (portfolio)   {Portfolio\\ rebalancing};
 \node [block, above=of portfolio] (policy) {Policy signalling};
 \node [block, above=of policy] (confidence) {Confidence};
 \node [block, below=of portfolio] (market) {Market liquidity};
 \node [block, below=of market] (money) {Money};
 \node [block, right=1cm of portfolio] (asset) {Asset prices\\ and the\\ exchange rate};
\node [block, right=1cm of money] (bank) {Bank lending};
\node [block, right=5cm of policy] (total) {Total wealth};
\node [block, right=5cm of market] (cost) {Cost of\\ borrowing};
\node [block, right=5cm of asset] (spending) {Spending and\\ income};
\node [block, right=1cm of spending] (inflation) {Inflation at 2\%};

\draw[->] (first) edge (portfolio);
\draw[->] (first.north) |- (policy.west);
\draw[->] (first.north) |- (confidence.west);   
\draw[->] (first.south) |- (market.west);
\draw[->] (first.south) |- (money.west);
\draw[->] (portfolio) edge (asset);
\draw[->] (policy.east) edge (asset.north);        
\draw[->] (market.east) edge (asset.south); 
\draw[->] (money) edge (bank);
\draw[<->] (bank.north) edge (asset.south);
\draw[->] (confidence.east) -| (asset.north);
\draw[->] (confidence.east) -| (spending.north);
\draw[->] (confidence.east) -| (inflation.north);
\draw[->] (asset.east) -| (total.south);
\draw[->] (asset.east) -| (cost.north);
\draw[->] (spending) edge (inflation);
\draw[->] (bank.east) -| (spending.south);
\draw[->] (total.east) -| (spending.north);
\draw[->] (cost.east) -| (spending.south);
\end{tikzpicture}

\end{document}

because I want to replicate the following diagram

and I am unable to place double arrows connected in a single block. I have also problems with the end of some connectors as you can check if you run the code.

Thanks in advance for your time!!!

Answer 1

You can define your arrow entry point by a certain angle around your node. So instead of saying spending.south you can say spending.270 which will result in the same. Knowing this, you can define whatever entry angle you desire.

I hope, this is what you meant:

% arara: pdflatex

\documentclass[tikz,border=5mm]{standalone}
\usetikzlibrary{arrows,positioning}
\usepackage{siunitx}

\begin{document}    
\begin{tikzpicture}[%
    ,node distance=5mm
    ,>=latex'
    ,block/.style = {%
        ,draw
        ,minimum height=10mm,minimum width=28mm
        ,align=center
        }
    ,every path/.style={->} 
    ]
    \node [block]                      (first)     {Bank of England\\ asset purchases};
    \node [block, right=of first]      (portfolio)   {Portfolio\\ rebalancing};
    \node [block, above=of portfolio] (policy) {Policy signalling};
    \node [block, above=of policy] (confidence) {Confidence};
    \node [block, below=of portfolio] (market) {Market liquidity};
    \node [block, below=of market] (money) {Money};
    \node [block, right=1cm of portfolio] (asset) {Asset prices\\ and the\\ exchange rate};
    \node [block, right=1cm of money] (bank) {Bank lending};
    \node [block, right=5cm of policy] (total) {Total wealth};
    \node [block, right=5cm of market] (cost) {Cost of\\ borrowing};
    \node [block, right=5cm of asset] (spending) {Spending and\\ income};
    \node [block, right=1cm of spending] (inflation) {Inflation at \SI{2}{\percent}};

    \draw (first) to (portfolio);
    \draw (first) |- (policy);
    \draw (first) |- (confidence);   
    \draw (first) |- (market);
    \draw (first) |- (money);
    \draw (portfolio) to (asset);
    \draw (policy.east) to (asset.140);        
    \draw (market.east) to (asset.220); 
    \draw (money) to (bank);
    \draw (money.10) to (asset.260);
    \draw[<->] (bank) to (asset);
    \draw (confidence) -| (asset);
    \draw (confidence) -| (spending.70);
    \draw (confidence) -| (inflation);
    \draw (asset) -| (total);
    \draw (asset) -| (cost);
    \draw (spending) to (inflation);
    \draw (bank) -| (spending.290);
    \draw (total) -| (spending.110);
    \draw (cost) -| (spending.250);
\end{tikzpicture}   
\end{document}

The edge syntax is for chains of arrows. You could save some lines of code (e.g. \draw (first) to (portfolio) edge (asset); if you connect several nodes in one chain at once. But I did not want to change your code too much and just replaced edge by to.

Answer 2

It does not really add much to the complete @LaRiFaRi answer but I wanted to show a different approach to define the ending point of a line using a convenient syntax provided by the library calc. Let's say you want to end the arrow between policy and asset at 1/4 of the distance between (asset.north west) and (asset.south west) (i.e. the left hand side of the rectangle wrapping the (asset) node). With the calc library you can easily do so:

\draw[->] (policy.east)--($(asset.north west)!.25!(asset.south west)$);

The syntax may appear tricky but in fact it's quite intuitive. You are after the node such that it is between (asset.north west) and (asset.south west) at 1/4=.25 of that distance; we wrap the calculation between dollar signs and the resulting point is in turn wrapped between parentheses. In other words the syntax would be: ($(first_node)!number_between_0_and_1!(second_node)$)

In a similar fashion you can also move from a point to a specified distance:

\draw[->] (policy.east)--($(asset.north west)+(0,-5mm)$);

that is, starting from (asset.north west) move downwards of a quantity equivalent to 5mm.

Of course you can do that using the notation (asset.<angle>) but it would involve some trigonometry and the result below could be hard to achieve (since there were only straight lines I've just used the -- notation between nodes to tackle the problem of the arrows):

\documentclass[tikz,border=5mm]{standalone}
    \usetikzlibrary{arrows,positioning,shapes,calc}
\usepackege{siunitx}
\begin{document}
\begin{tikzpicture}[node distance=5mm, >=latex',
 block/.style = {draw, rectangle, minimum height=10mm, minimum width=28mm,align=center},
tblock/.style = {draw, trapezium, minimum height=10mm, 
             trapezium left angle=75, trapezium right angle=105, align=center},
                        ]
 \node [block]                      (first)     {Bank of England\\ asset purchases};
 \node [block, right=of first]      (portfolio)   {Portfolio\\ rebalancing};
 \node [block, above=of portfolio] (policy) {Policy signalling};
 \node [block, above=of policy] (confidence) {Confidence};
 \node [block, below=of portfolio] (market) {Market liquidity};
 \node [block, below=of market] (money) {Money};
 \node [block, right=1cm of portfolio] (asset) {Asset prices\\ and the\\ exchange rate};
\node [block, right=1cm of money] (bank) {Bank lending};
\node [block, right=5cm of policy] (total) {Total wealth};
\node [block, right=5cm of market] (cost) {Cost of\\ borrowing};
\node [block, right=5cm of asset] (spending) {Spending and\\ income};
\node [block, right=1cm of spending] (inflation) {Inflation at \SI{2}{\percent}};

\draw[->] (first) edge (portfolio);
\draw[->] (first.north) |- (policy.west);
\draw[->] (first.north) |- (confidence.west);   
\draw[->] (first.south) |- (market.west);
\draw[->] (first.south) |- (money.west);
\draw[->] (portfolio) edge (asset);
\draw[->] (policy.east)--($(asset.west)!.5!(asset.north west)$);        
\draw[->] (market.east)--($(asset.south west)!.5!(asset.west)$); 
\draw[->] (money) edge (bank);
\draw[->] ($(money.east)+(0,2.5mm)$)--(asset.south west);
\draw[->] ($(confidence.east)+(0,-2.5mm)$)--(asset.north west);
\draw[<->] (bank.north) -- (asset.south);
\draw[->] (confidence.east) -| (asset.north);
\draw[->] (confidence.east) -| (spending.north);
\draw[->] (confidence.east) -| (inflation.north);
\draw[->] (asset.east) -| (total.south);
\draw[->] (asset.east) -| (cost.north);
\draw[->] (spending) edge (inflation);
\draw[->] (bank.east) -| (spending.south);
\draw[->] (total.east) -| (spending.north);
\draw[->] (cost.east) -| (spending.south);
\end{tikzpicture}
\end{document}