How to flush left alignments using alignat

Question

Could anyone help me align this multiline equation correctly? I am having very little luck. It is too long for one line, so I have spread it over 4 lines. I am trying to get all the +(#) terms after '\chemspec_\text{vit}' to be aligned to the left to remove the white space between the equations (so all the plus signs sit underneath each other).

\documentclass{article}
\usepackage[english]{babel} 
\usepackage{amsmath}

\begin{document}

% commands
\newcommand{\dydx}[2]{\frac{\text{d}#1}{\text{d}#2}}
\newcommand{\pRPEc}[1]{p_\text{RPE}^{(#1)}}
\newcommand{\pILMc}[1]{p_\text{ILM}^{(#1)}}
\newcommand{\kelc}[1]{k_\text{el}^{(#1)}}
\newcommand{\Sret}{S_\text{ret}}
\newcommand{\Vvit}{V_\text{vit}}
\newcommand{\SVit}{\frac{\Sret}{\Vvit}}
\newcommand{\konv}{k_\text{on}^{(v)}}
\newcommand{\koffv}{k_\text{off}^{(v)}}
\newcommand{\KDv}{K_\text{D}^{(v)}}
\newcommand{\konn}{k_\text{on}^{(n)}}
\newcommand{\koffn}{k_\text{off}^{(n)}}
\newcommand{\chemspec}{\R}
\newcommand{\area}{\text{ret}}
\newcommand{\V}{v}
\newcommand{\R}{r}
\newcommand{\VR}{c}
\newcommand{\RVR}{h}
\newcommand{\N}{n}
\newcommand{\RN}{m}
\newcommand{\VRN}{f}
\newcommand{\RVRN}{\left(n_0-\left\{\N+\RN+\VRN\right\}\right)}
\newcommand{\Rone}[1]  {\koffv \VR_#1 - 2\konv\V_#1\R_#1}   % R1
\newcommand{\Rtwo}[1]  {2\koffv \RVR_#1 - \konv\R_#1\VR_#1} % R2
\newcommand{\Rthree}[1]{\koffn \RN - \konn\R_#1\N}          % R3
\newcommand{\Rfivec}[1]{\koffv \RVRN - \konv\R_#1\VRN}      % R5c

\begin{alignat}{2}
% derivative
\dydx{\chemspec_\area}{t} &= 
% transfer
 \left(\SVit\right)\pILMc{\chemspec}\chemspec_\text{ret}                                % ret --> vit
-\left[\left(\SVit\right)\pILMc{\chemspec}+\kelc{\chemspec}\right]\chemspec_\text{vit}  % vit --> ret
% reactions
 &+\left(\Rone{\area}\right)\\              %  R1
&&+\left(\Rtwo{\area}\right)\nonumber\\     %  R2
&&+\left(\Rthree{\area}\right)\nonumber\\   %  R3
&&+\left(\Rfivec{\area}\right)\nonumber     %  R5c
\end{alignat}

\end{document}

EDIT: I explained that poorly, this is what I'm trying to achieve:

Unrelated: never use \text like this. Use for example _{\mathrm{...}} or use textup or textnormal instead of mathrm. The \text command does not do what you thing it does. This is a very common error. — daleif, Jan 11 '18 at 10:19

Andrew Swann · Accepted Answer · 2018-01-12 07:57:22Z

Just add one extra & to each of these lines:

\documentclass{article}
\usepackage[english]{babel}
\usepackage{amsmath,geometry}

\begin{document}

% commands
\newcommand{\dydx}[2]{\frac{\mathrm{d}#1}{\mathrm{d}#2}}
\newcommand{\pRPEc}[1]{p_{\mathrm{RPE}}^{(#1)}}
\newcommand{\pILMc}[1]{p_{\mathrm{ILM}}^{(#1)}}
\newcommand{\kelc}[1]{k_{\mathrm{el}}^{(#1)}}
\newcommand{\Sret}{S_{\mathrm{ret}}}
\newcommand{\Vvit}{V_{\mathrm{vit}}}
\newcommand{\SVit}{\frac{\Sret}{\Vvit}}
\newcommand{\konv}{k_{\mathrm{on}}^{(v)}}
\newcommand{\koffv}{k_{\mathrm{off}}^{(v)}}
\newcommand{\KDv}{K_{\mathrm{D}}^{(v)}}
\newcommand{\konn}{k_{\mathrm{on}}^{(n)}}
\newcommand{\koffn}{k_{\mathrm{off}}^{(n)}}
\newcommand{\chemspec}{\R}
\newcommand{\area}{\mathrm{ret}}
\newcommand{\V}{v}
\newcommand{\R}{r}
\newcommand{\VR}{c}
\newcommand{\RVR}{h}
\newcommand{\N}{n}
\newcommand{\RN}{m}
\newcommand{\VRN}{f}
\newcommand{\RVRN}{\bigl(n_0-\bigl\{\N+\RN+\VRN\bigr\}\bigr)}
\newcommand{\Rone}[1]  {\koffv \VR_#1 - 2\konv\V_#1\R_#1}   % R1
\newcommand{\Rtwo}[1]  {2\koffv \RVR_#1 - \konv\R_#1\VR_#1} % R2
\newcommand{\Rthree}[1]{\koffn \RN - \konn\R_#1\N}          % R3
\newcommand{\Rfivec}[1]{\koffv \RVRN - \konv\R_#1\VRN}      % R5c

\begin{alignat}{2}
% derivative
\dydx{\chemspec_\area}{t} &=
% transfer
 \Bigl(\SVit\Bigr)\pILMc{\chemspec}\chemspec_{\mathrm{ret}}                                % ret --> vit
-\Bigl[\Bigl(\SVit\Bigr)\pILMc{\chemspec}+\kelc{\chemspec}\Bigr]\chemspec_{\mathrm{vit}}  % vit --> ret
% reactions
 &&+\bigl(\Rone{\area}\bigr)\\              %  R1
&&&+\bigl(\Rtwo{\area}\bigr)\nonumber\\     %  R2
&&&+\bigl(\Rthree{\area}\bigr)\nonumber\\   %  R3
&&&+\bigl(\Rfivec{\area}\bigr)\nonumber     %  R3
\end{alignat}

\end{document}

The alignment of elements in alignat is

right & left & right & left & right & left ...

Other changes:

add geometry package to get your page width
used \mathrm instead of \text for consistent typesetting (\text changes with the surrounding formatting)
replaced \left...\right by specific sizing commands, \left...\right are often too big

You could instead consider using an aligned (e.g. as \begin{aligned}[t]) for the last block. That will make it easier to move to a new line if needed. E.g.

\documentclass{article}
\usepackage[english]{babel}
\usepackage{amsmath,geometry}

\begin{document}

% commands
\newcommand{\dydx}[2]{\frac{\mathrm{d}#1}{\mathrm{d}#2}}
\newcommand{\pRPEc}[1]{p_{\mathrm{RPE}}^{(#1)}}
\newcommand{\pILMc}[1]{p_{\mathrm{ILM}}^{(#1)}}
\newcommand{\kelc}[1]{k_{\mathrm{el}}^{(#1)}}
\newcommand{\Sret}{S_{\mathrm{ret}}}
\newcommand{\Vvit}{V_{\mathrm{vit}}}
\newcommand{\SVit}{\frac{\Sret}{\Vvit}}
\newcommand{\konv}{k_{\mathrm{on}}^{(v)}}
\newcommand{\koffv}{k_{\mathrm{off}}^{(v)}}
\newcommand{\KDv}{K_{\mathrm{D}}^{(v)}}
\newcommand{\konn}{k_{\mathrm{on}}^{(n)}}
\newcommand{\koffn}{k_{\mathrm{off}}^{(n)}}
\newcommand{\chemspec}{\R}
\newcommand{\area}{\mathrm{ret}}
\newcommand{\V}{v}
\newcommand{\R}{r}
\newcommand{\VR}{c}
\newcommand{\RVR}{h}
\newcommand{\N}{n}
\newcommand{\RN}{m}
\newcommand{\VRN}{f}
\newcommand{\RVRN}{\bigl(n_0-\bigl\{\N+\RN+\VRN\bigr\}\bigr)}
\newcommand{\Rone}[1]  {\koffv \VR_#1 - 2\konv\V_#1\R_#1}   % R1
\newcommand{\Rtwo}[1]  {2\koffv \RVR_#1 - \konv\R_#1\VR_#1} % R2
\newcommand{\Rthree}[1]{\koffn \RN - \konn\R_#1\N}          % R3
\newcommand{\Rfivec}[1]{\koffv \RVRN - \konv\R_#1\VRN}      % R5c

\begin{align}
  \dydx{\chemspec_\area}{t}
  &= \Bigl(\SVit\Bigr)\pILMc{\chemspec}\chemspec_{\mathrm{ret}}
    -\Bigl[\Bigl(\SVit\Bigr)\pILMc{\chemspec}+\kelc{\chemspec}\Bigr]
    \chemspec_{\mathrm{vit}}
    \begin{aligned}[t]
      &+\bigl(\Rone{\area}\bigr)\\
      &+\bigl(\Rtwo{\area}\bigr)\\
      &+\bigl(\Rthree{\area}\bigr)\\
      &+\bigl(\Rfivec{\area}\bigr)
    \end{aligned}
  \\
  &= \Bigl(\SVit\Bigr)\pILMc{\chemspec}\chemspec_{\mathrm{ret}}
    -\Bigl[\Bigl(\SVit\Bigr)\pILMc{\chemspec}+\kelc{\chemspec}\Bigr]
    \chemspec_{\mathrm{vit}}
  \\
  &\qquad
    \begin{aligned}[t]
      &+\bigl(\Rone{\area}\bigr)\\
      &+\bigl(\Rtwo{\area}\bigr)\\
      &+\bigl(\Rthree{\area}\bigr)\\
      &+\bigl(\Rfivec{\area}\bigr)
    \end{aligned}
        \nonumber
\end{align}

\end{document}

Ah that's awesome! Why the hell was I finding that so hard. Would you mind explaining why that works? — Freeman, Jan 11 '18 at 10:22
plus genereally not a good idea to use _\mathrm{...}, this feature does not work in general, so better to use _{\mathrm{...}} and ones main routine. — daleif, Jan 11 '18 at 10:27
AndrewSwann @daleif many thanks, I really appreciate the detailed and swift assistance. I've been trying to make this work for far too long. As you can see I need to learn quite a bit even after years of using LaTeX. — Freeman, Jan 11 '18 at 10:32
Uh! Isn't this just align with a single & per line in front of the + sign where alignment is needed? — egreg, Jan 11 '18 at 10:34
@egreg Yes, but the author may need to contiunue the alignment with further equalities... — Andrew Swann, Jan 11 '18 at 10:47

Bernard · Accepted Answer · 2018-01-11 10:58:35Z

I propose one of these three solutions. I loaded the geometry package to have more decent margins. Unrelated: the language options ofbabel` should be loaded with the document class options.

\documentclass[english]{article}
\usepackage{babel}
\usepackage{geometry}
\usepackage{mathtools}
\usepackage{showframe}
\renewcommand\ShowFrameLinethickness{0.3pt}

% commands
\newcommand{\dydx}[2]{\frac{\text{d}#1}{\text{d}#2}}
\newcommand{\pRPEc}[1]{p_\text{RPE}^{(#1)}}
\newcommand{\pILMc}[1]{p_\text{ILM}^{(#1)}}
\newcommand{\kelc}[1]{k_\text{el}^{(#1)}}
\newcommand{\Sret}{S_\text{ret}}
\newcommand{\Vvit}{V_\text{vit}}
\newcommand{\SVit}{\frac{\Sret}{\Vvit}}
\newcommand{\konv}{k_\text{on}^{(v)}}
\newcommand{\koffv}{k_\text{off}^{(v)}}
\newcommand{\KDv}{K_\text{D}^{(v)}}
\newcommand{\konn}{k_\text{on}^{(n)}}
\newcommand{\koffn}{k_\text{off}^{(n)}}
\newcommand{\chemspec}{\R}
\newcommand{\area}{\text{ret}}
\newcommand{\V}{v}
\newcommand{\R}{r}
\newcommand{\VR}{c}
\newcommand{\RVR}{h}
\newcommand{\N}{n}
\newcommand{\RN}{m}
\newcommand{\VRN}{f}
\newcommand{\RVRN}{\left(n_0-\left\{\N+\RN+\VRN\right\}\right)}
\newcommand{\Rone}[1] {\koffv \VR_#1 - 2\konv\V_#1\R_#1} % R1
\newcommand{\Rtwo}[1] {2\koffv \RVR_#1 - \konv\R_#1\VR_#1} % R2
\newcommand{\Rthree}[1]{\koffn \RN - \konn\R_#1\N} % R3
\newcommand{\Rfivec}[1]{\koffv \RVRN - \konv\R_#1\VRN} % R5c

\begin{document}

\begin{equation}
% derivative
 \begin{aligned}
  \dydx{\chemspec_\area}{t} =
% transfer
 \left(\SVit\right)\pILMc{\chemspec}\chemspec_\text{ret} % ret --> vit
 & -\left[\left(\SVit\right)\pILMc{\chemspec}+\kelc{\chemspec}\right]\chemspec_\text{vit} % vit --> ret
 % \\
% reactions
  +\left(\Rone{\area}\right)\\ % R1 &
  &+\left(\Rtwo{\area}\right)% \\ % R2
+\left(\Rthree{\area}\right) \\ % R3&
&+\left(\Rfivec{\area}\right) % R3
\end{aligned}
\end{equation}
\bigskip
\begin{align}
% derivative
  \dydx{\chemspec_\area}{t} =
% transfer
& \left(\SVit\right)\pILMc{\chemspec}\chemspec_\text{ret}% ret --> vit
 -\left[\left(\SVit\right)\pILMc{\chemspec}+\kelc{\chemspec}\right]\chemspec_\text{vit} % vit --> ret
 % \\
% reactions
  +\left(\Rone{\area}\right)\\ % R1
  &+\left(\Rtwo{\area}\right)% \\ % R2
+\left(\Rthree{\area}\right) % R3&
+\left(\Rfivec{\area}\right) % R3
\notag
\end{align}
\bigskip
\begin{equation}
% derivative
 \begin{aligned}
  \dydx{\chemspec_\area}{t} =
% transfer
 & \left(\SVit\right)\pILMc{\chemspec}\chemspec_\text{ret} % ret --> vit
 -\left[\left(\SVit\right)\pILMc{\chemspec}+\kelc{\chemspec}\right]\chemspec_\text{vit} % vit --> ret
  \\
% reactions
  & +\left(\Rone{\area}\right) % R1
   +\left(\Rtwo{\area}\right) \\ % R2
 & +\left(\Rthree{\area}\right) % R3
  +\left(\Rfivec{\area}\right) % R3
\end{aligned}
\end{equation}

\end{document}

Wow! Thanks so much Bernard :) This is really helpful! Learning a lot today. — Freeman, Jan 11 '18 at 11:14

Stack Exchange Network

current community

your communities

more stack exchange communities

How to flush left alignments using alignat

2 Answers 2

Your Answer

Not the answer you're looking for? Browse other questions tagged vertical-alignment align alignat or ask your own question.

Hot Network Questions

How to flush left alignments using alignat

2 Answers 2

Your Answer

Sign up or log in

Post as a guest

Not the answer you're looking for? Browse other questions tagged vertical-alignment align alignat or ask your own question.

Related

Hot Network Questions